=========================
Django 1.10 release notes
=========================

*August 1, 2016*

Welcome to Django 1.10!

These release notes cover the :ref:`new features <whats-new-1.10>`, as well as
some :ref:`backwards incompatible changes <backwards-incompatible-1.10>` you'll
want to be aware of when upgrading from Django 1.9 or older versions. We've
:ref:`dropped some features <removed-features-1.10>` that have reached the end
of their deprecation cycle, and we've :ref:`begun the deprecation process for
some features <deprecated-features-1.10>`.

See the :doc:`/howto/upgrade-version` guide if you're updating an existing
project.

Python compatibility
====================

Like Django 1.9, Django 1.10 requires Python 2.7, 3.4, or 3.5. We **highly
recommend** and only officially support the latest release of each series.

.. _whats-new-1.10:

What's new in Django 1.10
=========================

Full text search for PostgreSQL
-------------------------------

``django.contrib.postgres`` now includes a :doc:`collection of database
functions </ref/contrib/postgres/search>` to allow the use of the full text
search engine. You can search across multiple fields in your relational
database, combine the searches with other lookups, use different language
configurations and weightings, and rank the results by relevance.

It also now includes trigram support, using the :lookup:`trigram_similar`
lookup, and the :class:`~django.contrib.postgres.search.TrigramSimilarity` and
:class:`~django.contrib.postgres.search.TrigramDistance` expressions.

New-style middleware
--------------------

:doc:`A new style of middleware is introduced </topics/http/middleware>` to
solve the lack of strict request/response layering of the old-style of
middleware described in `DEP 0005
<https://github.com/django/deps/blob/master/final/0005-improved-middleware.rst>`_.
You'll need to :ref:`adapt old, custom middleware <upgrading-middleware>` and
switch from the ``MIDDLEWARE_CLASSES`` setting to the new :setting:`MIDDLEWARE`
setting to take advantage of the improvements.

Official support for Unicode usernames
--------------------------------------

The :class:`~django.contrib.auth.models.User` model in ``django.contrib.auth``
originally only accepted ASCII letters in usernames. Although it wasn't a
deliberate choice, Unicode characters have always been accepted when using
Python 3.

The username validator now explicitly accepts Unicode letters by
default on Python 3 only. This default behavior can be overridden by changing
the :attr:`~django.contrib.auth.models.User.username_validator` attribute of
the ``User`` model, or to any proxy of that model, using either
:class:`~django.contrib.auth.validators.ASCIIUsernameValidator` or
:class:`~django.contrib.auth.validators.UnicodeUsernameValidator`. Custom user
models may also use those validators.

Minor features
--------------

:mod:`django.contrib.admin`
~~~~~~~~~~~~~~~~~~~~~~~~~~~

* For sites running on a subpath, the default :attr:`URL for the "View site"
  link <django.contrib.admin.AdminSite.site_url>` at the top of each admin page
  will now point to ``request.META['SCRIPT_NAME']`` if set, instead of ``/``.

* The success message that appears after adding or editing an object now
  contains a link to the object's change form.

* All inline JavaScript is removed so you can enable the
  ``Content-Security-Policy`` HTTP header if you wish.

* The new :attr:`InlineModelAdmin.classes
  <django.contrib.admin.InlineModelAdmin.classes>` attribute allows specifying
  classes on inline fieldsets. Inlines with a ``collapse`` class will be
  initially collapsed and their header will have a small "show" link.

* If a user doesn't have the add permission, the ``object-tools`` block on a
  model's changelist will now be rendered (without the add button, of course).
  This makes it easier to add custom tools in this case.

* The :class:`~django.contrib.admin.models.LogEntry` model now stores change
  messages in a JSON structure so that the message can be dynamically translated
  using the current active language. A new ``LogEntry.get_change_message()``
  method is now the preferred way of retrieving the change message.

* Selected objects for fields in ``ModelAdmin.raw_id_fields`` now have a link
  to object's change form.

* Added "No date" and "Has date" choices for ``DateFieldListFilter`` if the
  field is nullable.

* The jQuery library embedded in the admin is upgraded from version 2.1.4 to
  2.2.3.

:mod:`django.contrib.auth`
~~~~~~~~~~~~~~~~~~~~~~~~~~

* Added support for the :ref:`Argon2 password hash <argon2_usage>`. It's
  recommended over PBKDF2, however, it's not the default as it requires a
  third-party library.

* The default iteration count for the PBKDF2 password hasher has been increased
  by 25%. This backwards compatible change will not affect users who have
  subclassed ``django.contrib.auth.hashers.PBKDF2PasswordHasher`` to change the
  default value.

* The :func:`~django.contrib.auth.views.logout` view sends "no-cache" headers
  to prevent an issue where Safari caches redirects and prevents a user from
  being able to log out.

* Added the optional ``backend`` argument to :func:`~django.contrib.auth.login`
  to allow using it without credentials.

* The new :setting:`LOGOUT_REDIRECT_URL` setting controls the redirect of the
  :func:`~django.contrib.auth.views.logout` view, if the view doesn't get a
  ``next_page`` argument.

* The new ``redirect_authenticated_user`` parameter for the
  :func:`~django.contrib.auth.views.login` view allows redirecting
  authenticated users visiting the login page.

* The new :class:`~django.contrib.auth.backends.AllowAllUsersModelBackend` and
  :class:`~django.contrib.auth.backends.AllowAllUsersRemoteUserBackend` ignore
  the value of ``User.is_active``, while
  :class:`~django.contrib.auth.backends.ModelBackend` and
  :class:`~django.contrib.auth.backends.RemoteUserBackend` now reject inactive
  users.

:mod:`django.contrib.gis`
~~~~~~~~~~~~~~~~~~~~~~~~~

* :ref:`Distance lookups <distance-lookups>` now accept expressions as the
  distance value parameter.

* The new :attr:`GEOSGeometry.unary_union
  <django.contrib.gis.geos.GEOSGeometry.unary_union>` property computes the
  union of all the elements of this geometry.

* Added the :meth:`GEOSGeometry.covers()
  <django.contrib.gis.geos.GEOSGeometry.covers>` binary predicate.

* Added the :meth:`GDALBand.statistics()
  <django.contrib.gis.gdal.GDALBand.statistics>` method and
  :attr:`~django.contrib.gis.gdal.GDALBand.mean`
  and :attr:`~django.contrib.gis.gdal.GDALBand.std` attributes.

* Added support for the :class:`~django.contrib.gis.db.models.MakeLine`
  aggregate and :class:`~django.contrib.gis.db.models.functions.GeoHash`
  function on SpatiaLite.

* Added support for the
  :class:`~django.contrib.gis.db.models.functions.Difference`,
  :class:`~django.contrib.gis.db.models.functions.Intersection`, and
  :class:`~django.contrib.gis.db.models.functions.SymDifference`
  functions on MySQL.

* Added support for instantiating empty GEOS geometries.

* The new :attr:`~django.contrib.gis.geos.WKTWriter.trim` and
  :attr:`~django.contrib.gis.geos.WKTWriter.precision` properties
  of :class:`~django.contrib.gis.geos.WKTWriter` allow controlling
  output of the fractional part of the coordinates in WKT.

* Added the :attr:`LineString.closed
  <django.contrib.gis.geos.LineString.closed>` and
  :attr:`MultiLineString.closed
  <django.contrib.gis.geos.MultiLineString.closed>` properties.

* The :doc:`GeoJSON serializer </ref/contrib/gis/serializers>` now outputs the
  primary key of objects in the ``properties`` dictionary if specific fields
  aren't specified.

* The ability to replicate input data on the :meth:`GDALBand.data()
  <django.contrib.gis.gdal.GDALBand.data>` method was added. Band data can
  now be updated with repeated values efficiently.

* Added database functions
  :class:`~django.contrib.gis.db.models.functions.IsValid` and
  :class:`~django.contrib.gis.db.models.functions.MakeValid`, as well as the
  :lookup:`isvalid` lookup, all for PostGIS. This allows filtering and
  repairing invalid geometries on the database side.

* Added raster support for all :doc:`spatial lookups
  </ref/contrib/gis/geoquerysets>`.

:mod:`django.contrib.postgres`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* For convenience, :class:`~django.contrib.postgres.fields.HStoreField` now
  casts its keys and values to strings.

:mod:`django.contrib.sessions`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The :djadmin:`clearsessions` management command now removes file-based
  sessions.

:mod:`django.contrib.sites`
~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The :class:`~django.contrib.sites.models.Site` model now supports
  :ref:`natural keys <topics-serialization-natural-keys>`.

:mod:`django.contrib.staticfiles`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The :ttag:`static` template tag now uses ``django.contrib.staticfiles``
  if it's in ``INSTALLED_APPS``. This is especially useful for third-party apps
  which can now always use ``{% load static %}`` (instead of
  ``{% load staticfiles %}`` or ``{% load static from staticfiles %}``) and
  not worry about whether or not the ``staticfiles`` app is installed.

* You can :ref:`more easily customize <customize-staticfiles-ignore-patterns>`
  the ``collectstatic --ignore_patterns`` option with a custom ``AppConfig``.

Cache
~~~~~

* The file-based cache backend now uses the highest pickling protocol.

CSRF
~~~~

* The default :setting:`CSRF_FAILURE_VIEW`, ``views.csrf.csrf_failure()`` now
  accepts an optional ``template_name`` parameter, defaulting to
  ``'403_csrf.html'``, to control the template used to render the page.

* To protect against `BREACH`_ attacks, the CSRF protection mechanism now
  changes the form token value on every request (while keeping an invariant
  secret which can be used to validate the different tokens).

.. _BREACH: http://breachattack.com/

Database backends
~~~~~~~~~~~~~~~~~

* Temporal data subtraction was unified on all backends.

* If the database supports it, backends can set
  ``DatabaseFeatures.can_return_ids_from_bulk_insert=True`` and implement
  ``DatabaseOperations.fetch_returned_insert_ids()`` to set primary keys
  on objects created using ``QuerySet.bulk_create()``.

* Added keyword arguments to the ``as_sql()`` methods of various expressions
  (``Func``, ``When``, ``Case``, and ``OrderBy``) to allow database backends to
  customize them without mutating ``self``, which isn't safe when using
  different database backends. See the ``arg_joiner`` and ``**extra_context``
  parameters of :meth:`Func.as_sql() <django.db.models.Func.as_sql>` for an
  example.

File Storage
~~~~~~~~~~~~

* Storage backends now present a timezone-aware API with new methods
  :meth:`~django.core.files.storage.Storage.get_accessed_time`,
  :meth:`~django.core.files.storage.Storage.get_created_time`, and
  :meth:`~django.core.files.storage.Storage.get_modified_time`. They return a
  timezone-aware ``datetime`` if :setting:`USE_TZ` is ``True`` and a naive
  ``datetime`` in the local timezone otherwise.

* The new :meth:`Storage.generate_filename()
  <django.core.files.storage.Storage.generate_filename>` method makes it easier
  to implement custom storages that don't use the ``os.path`` calls previously
  in :class:`~django.db.models.FileField`.

Forms
~~~~~

* Form and widget ``Media`` is now served using
  :mod:`django.contrib.staticfiles` if installed.

* The ``<input>`` tag rendered by :class:`~django.forms.CharField` now includes
  a ``minlength`` attribute if the field has a ``min_length``.

* Required form fields now have the ``required`` HTML attribute. Set the new
  :attr:`Form.use_required_attribute <django.forms.Form.use_required_attribute>`
  attribute to ``False`` to disable it. The ``required`` attribute isn't
  included on forms of formsets because the browser validation may not be
  correct when adding and deleting formsets.

Generic Views
~~~~~~~~~~~~~

* The :class:`~django.views.generic.base.View` class can now be imported from
  ``django.views``.

Internationalization
~~~~~~~~~~~~~~~~~~~~

* The :func:`~django.conf.urls.i18n.i18n_patterns` helper function can now be
  used in a root URLConf specified using :attr:`request.urlconf
  <django.http.HttpRequest.urlconf>`.

* By setting the new ``prefix_default_language`` parameter for
  :func:`~django.conf.urls.i18n.i18n_patterns` to ``False``, you can allow
  accessing the default language without a URL prefix.

* :func:`~django.views.i18n.set_language` now returns a 204 status code (No
  Content) for AJAX requests when there is no ``next`` parameter in ``POST`` or
  ``GET``.

* The :class:`~django.views.i18n.JavaScriptCatalog` and
  :class:`~django.views.i18n.JSONCatalog` class-based views supersede the
  deprecated ``javascript_catalog()`` and ``json_catalog()`` function-based
  views. The new views are almost equivalent to the old ones except that by
  default the new views collect all JavaScript strings in the ``djangojs``
  translation domain from all installed apps rather than only the JavaScript
  strings from :setting:`LOCALE_PATHS`.

Management Commands
~~~~~~~~~~~~~~~~~~~

* :func:`~django.core.management.call_command` now returns the value returned
  from the ``command.handle()`` method.

* The new :option:`check --fail-level` option allows specifying the message
  level that will cause the command to exit with a non-zero status.

* The new :option:`makemigrations --check` option makes the command exit
  with a non-zero status when model changes without migrations are detected.

* :djadmin:`makemigrations` now displays the path to the migration files that
  it generates.

* The :option:`shell --interface` option now accepts ``python`` to force use of
  the "plain" Python interpreter.

* The new :option:`shell --command` option lets you run a command as Django and
  exit, instead of opening the interactive shell.

* Added a warning to :djadmin:`dumpdata` if a proxy model is specified (which
  results in no output) without its concrete parent.

* The new :attr:`BaseCommand.requires_migrations_checks
  <django.core.management.BaseCommand.requires_migrations_checks>` attribute
  may be set to ``True`` if you want your command to print a warning, like
  :djadmin:`runserver` does, if the set of migrations on disk don't match the
  migrations in the database.

* To assist with testing, :func:`~django.core.management.call_command` now
  accepts a command object as the first argument.

* The :djadmin:`shell` command supports tab completion on systems using
  ``libedit``, e.g. Mac OSX.

* The :djadmin:`inspectdb` command lets you choose what tables should be
  inspected by specifying their names as arguments.

Migrations
~~~~~~~~~~

* Added support for serialization of ``enum.Enum`` objects.

* Added the ``elidable`` argument to the
  :class:`~django.db.migrations.operations.RunSQL` and
  :class:`~django.db.migrations.operations.RunPython` operations to allow them
  to be removed when squashing migrations.

* Added support for :ref:`non-atomic migrations <non-atomic-migrations>` by
  setting the ``atomic`` attribute on a ``Migration``.

* The ``migrate`` and ``makemigrations`` commands now check for a consistent
  migration history. If they find some unapplied dependencies of an applied
  migration, ``InconsistentMigrationHistory`` is raised.

* The :func:`~django.db.models.signals.pre_migrate` and
  :func:`~django.db.models.signals.post_migrate` signals now dispatch their
  migration ``plan`` and ``apps``.

Models
~~~~~~

* Reverse foreign keys from proxy models are now propagated to their
  concrete class. The reverse relation attached by a
  :class:`~django.db.models.ForeignKey` pointing to a proxy model is now
  accessible as a descriptor on the proxied model class and may be referenced in
  queryset filtering.

* The new :meth:`Field.rel_db_type() <django.db.models.Field.rel_db_type>`
  method returns the database column data type for fields such as ``ForeignKey``
  and ``OneToOneField`` that point to another field.

* The :attr:`~django.db.models.Func.arity` class attribute is added to
  :class:`~django.db.models.Func`. This attribute can be used to set the number
  of arguments the function accepts.

* Added :class:`~django.db.models.BigAutoField` which acts much like an
  :class:`~django.db.models.AutoField` except that it is guaranteed
  to fit numbers from ``1`` to ``9223372036854775807``.

* :meth:`QuerySet.in_bulk() <django.db.models.query.QuerySet.in_bulk>`
  may be called without any arguments to return all objects in the queryset.

* :attr:`~django.db.models.ForeignKey.related_query_name` now supports
  app label and class interpolation using the ``'%(app_label)s'`` and
  ``'%(class)s'`` strings.

* Allowed overriding model fields inherited from abstract base classes.

* The :func:`~django.db.models.prefetch_related_objects` function is now a
  public API.

* :meth:`QuerySet.bulk_create() <django.db.models.query.QuerySet.bulk_create>`
  sets the primary key on objects when using PostgreSQL.

* Added the :class:`~django.db.models.functions.Cast` database function.

* A proxy model may now inherit multiple proxy models that share a common
  non-abstract parent class.

* Added :class:`~django.db.models.functions.datetime.Extract` functions
  to extract datetime components as integers, such as year and hour.

* Added :class:`~django.db.models.functions.datetime.Trunc` functions to
  truncate a date or datetime to a significant component. They enable queries
  like sales-per-day or sales-per-hour.

* ``Model.__init__()`` now sets values of virtual fields from its keyword
  arguments.

* The new :attr:`Meta.base_manager_name
  <django.db.models.Options.base_manager_name>` and
  :attr:`Meta.default_manager_name
  <django.db.models.Options.default_manager_name>` options allow controlling
  the :attr:`~django.db.models.Model._base_manager` and
  :attr:`~django.db.models.Model._default_manager`, respectively.

Requests and Responses
~~~~~~~~~~~~~~~~~~~~~~

* Added ``request.user`` to the debug view.

* Added :class:`~django.http.HttpResponse` methods
  :meth:`~django.http.HttpResponse.readable()` and
  :meth:`~django.http.HttpResponse.seekable()` to make an instance a
  stream-like object and allow wrapping it with :py:class:`io.TextIOWrapper`.

* Added the :attr:`HttpResponse.content_type
  <django.http.HttpRequest.content_type>` and
  :attr:`~django.http.HttpRequest.content_params` attributes which are
  parsed from the ``CONTENT_TYPE`` header.

* The parser for ``request.COOKIES`` is simplified to better match the behavior
  of browsers. ``request.COOKIES`` may now contain cookies that are invalid
  according to :rfc:`6265` but are possible to set via ``document.cookie``.

Serialization
~~~~~~~~~~~~~

* The ``django.core.serializers.json.DjangoJSONEncoder`` now knows how to
  serialize lazy strings, typically used for translatable content.

Templates
~~~~~~~~~

* Added the ``autoescape`` option to the
  :class:`~django.template.backends.django.DjangoTemplates` backend and the
  :class:`~django.template.Engine` class.

* Added the ``is`` and ``is not`` comparison operators to the :ttag:`if` tag.

* Allowed :tfilter:`dictsort` to order a list of lists by an element at a
  specified index.

* The :func:`~django.template.context_processors.debug` context processor
  contains queries for all database aliases instead of only the default alias.

* Added relative path support for string arguments of the :ttag:`extends` and
  :ttag:`include` template tags.

Tests
~~~~~

* To better catch bugs, :class:`~django.test.TestCase` now checks deferrable
  database constraints at the end of each test.

* Tests and test cases can be :ref:`marked with tags <topics-tagging-tests>`
  and run selectively with the new :option:`test --tag` and :option:`test
  --exclude-tag` options.

* You can now login and use sessions with the test client even if
  :mod:`django.contrib.sessions` is not in :setting:`INSTALLED_APPS`.

URLs
~~~~

* An addition in :func:`django.setup()` allows URL resolving that happens
  outside of the request/response cycle (e.g. in management commands and
  standalone scripts) to take :setting:`FORCE_SCRIPT_NAME` into account when it
  is set.

Validators
~~~~~~~~~~

* :class:`~django.core.validators.URLValidator` now limits the length of
  domain name labels to 63 characters and the total length of domain
  names to 253 characters per :rfc:`1034`.

* :func:`~django.core.validators.int_list_validator` now accepts an optional
  ``allow_negative`` boolean parameter, defaulting to ``False``, to allow
  negative integers.

.. _backwards-incompatible-1.10:

Backwards incompatible changes in 1.10
======================================

.. warning::

    In addition to the changes outlined in this section, be sure to review the
    :ref:`removed-features-1.10` for the features that have reached the end of
    their deprecation cycle and therefore been removed. If you haven't updated
    your code within the deprecation timeline for a given feature, its removal
    may appear as a backwards incompatible change.

Database backend API
--------------------

* GIS's ``AreaField`` uses an unspecified underlying numeric type that could in
  practice be any numeric Python type. ``decimal.Decimal`` values retrieved
  from the database are now converted to ``float`` to make it easier to combine
  them with values used by the GIS libraries.

* In order to enable temporal subtraction you must set the
  ``supports_temporal_subtraction`` database feature flag to ``True`` and
  implement the ``DatabaseOperations.subtract_temporals()`` method. This
  method should return the SQL and parameters required to compute the
  difference in microseconds between the ``lhs`` and ``rhs`` arguments in the
  datatype used to store :class:`~django.db.models.DurationField`.

``select_related()`` prohibits non-relational fields for nested relations
-------------------------------------------------------------------------

Django 1.8 added validation for non-relational fields in ``select_related()``::

    >>> Book.objects.select_related('title')
    Traceback (most recent call last):
    ...
    FieldError: Non-relational field given in select_related: 'title'

But it didn't prohibit nested non-relation fields as it does now::

    >>> Book.objects.select_related('author__name')
    Traceback (most recent call last):
    ...
    FieldError: Non-relational field given in select_related: 'name'

``_meta.get_fields()`` returns consistent reverse fields for proxy models
-------------------------------------------------------------------------

Before Django 1.10, the :meth:`~django.db.models.options.Options.get_fields`
method returned different reverse fields when called on a proxy model compared
to its proxied concrete class. This inconsistency was fixed by returning the
full set of fields pointing to a concrete class or one of its proxies in both
cases.

:attr:`AbstractUser.username <django.contrib.auth.models.User.username>` ``max_length`` increased to 150
--------------------------------------------------------------------------------------------------------

A migration for :attr:`django.contrib.auth.models.User.username` is included.
If you have a custom user model inheriting from ``AbstractUser``, you'll need
to generate and apply a database migration for your user model.

We considered an increase to 254 characters to more easily allow the use of
email addresses (which are limited to 254 characters) as usernames but rejected
it due to a MySQL limitation.  When using the ``utf8mb4`` encoding (recommended
for proper Unicode support), MySQL can only create unique indexes with 191
characters by default. Therefore, if you need a longer length, please use a
custom user model.

If you want to preserve the 30 character limit for usernames, use a custom form
when creating a user or changing usernames::

    from django.contrib.auth.forms import UserCreationForm

    class MyUserCreationForm(UserCreationForm):
        username = forms.CharField(
            max_length=30,
            help_text='Required. 30 characters or fewer. Letters, digits and @/./+/-/_ only.',
        )

If you wish to keep this restriction in the admin, set ``UserAdmin.add_form``
to use this form::

    from django.contrib.auth.admin import UserAdmin as BaseUserAdmin
    from django.contrib.auth.models import User

    class UserAdmin(BaseUserAdmin):
        add_form = MyUserCreationForm

    admin.site.unregister(User)
    admin.site.register(User, UserAdmin)

Dropped support for PostgreSQL 9.1
----------------------------------

Upstream support for PostgreSQL 9.1 ends in September 2016. As a consequence,
Django 1.10 sets PostgreSQL 9.2 as the minimum version it officially supports.

``runserver`` output goes through logging
-----------------------------------------

Request and response handling of the ``runserver`` command is sent to the
:ref:`django-server-logger` logger instead of to ``sys.stderr``. If you
disable Django's logging configuration or override it with your own, you'll
need to add the appropriate logging configuration if you want to see that
output::

    'formatters': {
        'django.server': {
            '()': 'django.utils.log.ServerFormatter',
            'format': '[%(server_time)s] %(message)s',
        }
    },
    'handlers': {
        'django.server': {
            'level': 'INFO',
            'class': 'logging.StreamHandler',
            'formatter': 'django.server',
        },
    },
    'loggers': {
        'django.server': {
            'handlers': ['django.server'],
            'level': 'INFO',
            'propagate': False,
        }
    }

``auth.CustomUser`` and ``auth.ExtensionUser`` test models were removed
-----------------------------------------------------------------------

Since the introduction of migrations for the contrib apps in Django 1.8, the
tables of these custom user test models were not created anymore making them
unusable in a testing context.

Apps registry is no longer auto-populated when unpickling models outside of Django
----------------------------------------------------------------------------------

The apps registry is no longer auto-populated when unpickling models. This was
added in Django 1.7.2 as an attempt to allow unpickling models outside of
Django, such as in an RQ worker, without calling ``django.setup()``, but it
creates the possibility of a deadlock. To adapt your code in the case of RQ,
you can `provide your own worker script <http://python-rq.org/docs/workers/>`_
that calls ``django.setup()``.

Removed null assignment check for non-null foreign key fields
-------------------------------------------------------------

In older versions, assigning ``None`` to a non-nullable ``ForeignKey`` or
``OneToOneField`` raised ``ValueError('Cannot assign None: "model.field" does
not allow null values.')``. For consistency with other model fields which don't
have a similar check, this check is removed.

Removed weak password hashers from the default ``PASSWORD_HASHERS`` setting
---------------------------------------------------------------------------

Django 0.90 stored passwords as unsalted MD5. Django 0.91 added support for
salted SHA1 with automatic upgrade of passwords when a user logs in. Django 1.4
added PBKDF2 as the default password hasher.

If you have an old Django project with MD5 or SHA1 (even salted) encoded
passwords, be aware that these can be cracked fairly easily with today's
hardware. To make Django users acknowledge continued use of weak hashers, the
following hashers are removed from the default :setting:`PASSWORD_HASHERS`
setting::

    'django.contrib.auth.hashers.SHA1PasswordHasher'
    'django.contrib.auth.hashers.MD5PasswordHasher'
    'django.contrib.auth.hashers.UnsaltedSHA1PasswordHasher'
    'django.contrib.auth.hashers.UnsaltedMD5PasswordHasher'
    'django.contrib.auth.hashers.CryptPasswordHasher'

Consider using a :ref:`wrapped password hasher <wrapping-password-hashers>` to
strengthen the hashes in your database. If that's not feasible, add the
:setting:`PASSWORD_HASHERS` setting to your project and add back any hashers
that you need.

You can check if your database has any of the removed hashers like this::

    from django.contrib.auth import get_user_model
    User = get_user_model()

    # Unsalted MD5/SHA1:
    User.objects.filter(password__startswith='md5$$')
    User.objects.filter(password__startswith='sha1$$')
    # Salted MD5/SHA1:
    User.objects.filter(password__startswith='md5$').exclude(password__startswith='md5$$')
    User.objects.filter(password__startswith='sha1$').exclude(password__startswith='sha1$$')
    # Crypt hasher:
    User.objects.filter(password__startswith='crypt$$')

    from django.db.models import CharField
    from django.db.models.functions import Length
    CharField.register_lookup(Length)
    # Unsalted MD5 passwords might not have an 'md5$$' prefix:
    User.objects.filter(password__length=32)

``Field.get_prep_lookup()`` and ``Field.get_db_prep_lookup()`` methods are removed
----------------------------------------------------------------------------------

If you have a custom field that implements either of these methods, register a
custom lookup for it. For example::

    from django.db.models import Field
    from django.db.models.lookups import Exact

    class MyField(Field):
        ...

    class MyFieldExact(Exact):
        def get_prep_lookup(self):
            # do_custom_stuff_for_myfield
            ....

    MyField.register_lookup(MyFieldExact)

:mod:`django.contrib.gis`
-------------------------

* Support for SpatiaLite < 3.0 and GEOS < 3.3 is dropped.

* The ``add_postgis_srs()`` backwards compatibility alias for
  ``django.contrib.gis.utils.add_srs_entry()`` is removed.

* On Oracle/GIS, the :class:`~django.contrib.gis.db.models.functions.Area`
  aggregate function now returns a ``float`` instead of ``decimal.Decimal``.
  (It's still wrapped in a measure of square meters.)

* The default :class:`~django.contrib.gis.geos.GEOSGeometry` representation (WKT
  output) is trimmed by default. That is, instead of
  ``POINT (23.0000000000000000 5.5000000000000000)``, you'll get
  ``POINT (23 5.5)``.

Maximum size of a request body and the number of GET/POST parameters is limited
-------------------------------------------------------------------------------

Two new settings help mitigate denial-of-service attacks via large requests:

* :setting:`DATA_UPLOAD_MAX_MEMORY_SIZE` limits the size that a request body
  may be. File uploads don't count towards this limit.
* :setting:`DATA_UPLOAD_MAX_NUMBER_FIELDS` limits the number of GET/POST
  parameters that are parsed.

Applications that receive unusually large form posts may need to tune these
settings.

Miscellaneous
-------------

* The ``repr()`` of a ``QuerySet`` is wrapped in ``<QuerySet >`` to
  disambiguate it from a plain list when debugging.

* ``utils.version.get_version()`` returns :pep:`440` compliant release
  candidate versions (e.g. '1.10rc1' instead of '1.10c1').

* CSRF token values are now required to be strings of 64 alphanumerics; values
  of 32 alphanumerics, as set by older versions of Django by default, are
  automatically replaced by strings of 64 characters. Other values are
  considered invalid. This should only affect developers or users who replace
  these tokens.

* The ``LOGOUT_URL`` setting is removed as Django hasn't made use of it
  since pre-1.0. If you use it in your project, you can add it to your
  project's settings. The default value was ``'/accounts/logout/'``.

* Objects with a ``close()`` method such as files and generators passed to
  :class:`~django.http.HttpResponse` are now closed immediately instead of when
  the WSGI server calls ``close()`` on the response.

* A redundant ``transaction.atomic()`` call in ``QuerySet.update_or_create()``
  is removed. This may affect query counts tested by
  ``TransactionTestCase.assertNumQueries()``.

* Support for ``skip_validation`` in ``BaseCommand.execute(**options)`` is
  removed. Use ``skip_checks`` (added in Django 1.7) instead.

* :djadmin:`loaddata` now raises a ``CommandError`` instead of showing a
  warning when the specified fixture file is not found.

* Instead of directly accessing the ``LogEntry.change_message`` attribute, it's
  now better to call the ``LogEntry.get_change_message()`` method which will
  provide the message in the current language.

* The default error views now raise ``TemplateDoesNotExist`` if a nonexistent
  ``template_name`` is specified.

* The unused ``choices`` keyword argument of the ``Select`` and
  ``SelectMultiple`` widgets' ``render()`` method is removed. The ``choices``
  argument of the ``render_options()`` method is also removed, making
  ``selected_choices`` the first argument.

* Tests that violate deferrable database constraints will now error when run on
  a database that supports deferrable constraints.

* Built-in management commands now use indexing of keys in ``options``, e.g.
  ``options['verbosity']``, instead of ``options.get()`` and no longer perform
  any type coercion. This could be a problem if you're calling commands using
  ``Command.execute()`` (which bypasses the argument parser that sets a default
  value) instead of :func:`~django.core.management.call_command`. Instead of
  calling ``Command.execute()``, pass the command object as the first argument
  to ``call_command()``.

* :class:`~django.contrib.auth.backends.ModelBackend` and
  :class:`~django.contrib.auth.backends.RemoteUserBackend` now reject inactive
  users. This means that inactive users can't login and will be logged
  out if they are switched from ``is_active=True`` to ``False``. If you need
  the previous behavior, use the new
  :class:`~django.contrib.auth.backends.AllowAllUsersModelBackend` or
  :class:`~django.contrib.auth.backends.AllowAllUsersRemoteUserBackend`
  in :setting:`AUTHENTICATION_BACKENDS` instead.

* In light of the previous change, the test client's
  :meth:`~django.test.Client.login()` method no longer always rejects inactive
  users but instead delegates this decision to the authentication backend.
  :meth:`~django.test.Client.force_login()` also delegates the decision to the
  authentication backend, so if you're using the default backends, you need to
  use an active user.

* :func:`django.views.i18n.set_language` may now return a 204 status code for
  AJAX requests.

* The ``base_field`` attribute of
  :class:`~django.contrib.postgres.fields.RangeField` is now a type of field,
  not an instance of a field.  If you have created a custom subclass of
  :class:`~django.contrib.postgres.fields.RangeField`, you should change the
  ``base_field`` attribute.

* Middleware classes are now initialized when the server starts rather than
  during the first request.

* If you override ``is_authenticated()`` or ``is_anonymous()`` in a custom user
  model, you must convert them to attributes or properties as described in
  :ref:`the deprecation note <user-is-auth-anon-deprecation>`.

* When using :attr:`ModelAdmin.save_as=True
  <django.contrib.admin.ModelAdmin.save_as>`, the "Save as new" button now
  redirects to the change view for the new object instead of to the model's
  changelist. If you need the previous behavior, set the new
  :attr:`ModelAdmin.save_as_continue
  <django.contrib.admin.ModelAdmin.save_as_continue>` attribute to ``False``.

* Required form fields now have the ``required`` HTML attribute. Set the
  :attr:`Form.use_required_attribute <django.forms.Form.use_required_attribute>`
  attribute to ``False`` to disable it. You could also add the ``novalidate``
  attribute to ``<form>`` if you don't want browser validation.

* The WSGI handler no longer removes content of responses from ``HEAD``
  requests or responses with a ``status_code`` of 100-199, 204, or 304. Most
  Web servers already implement this behavior. Responses retrieved using the
  Django test client continue to have these "response fixes" applied.

* ``Model.__init__()`` now receives ``django.db.models.DEFERRED`` as the value
  of deferred fields.

* The ``Model._deferred`` attribute is removed as dynamic model classes when
  using ``QuerySet.defer()`` and ``only()`` is removed.

* :meth:`Storage.save() <django.core.files.storage.Storage.save>` no longer
  replaces ``'\'`` with ``'/'``. This behavior is moved to
  :class:`~django.core.files.storage.FileSystemStorage` since this is a storage
  specific implementation detail. Any Windows user with a custom storage
  implementation that relies on this behavior will need to implement it in the
  custom storage's ``save()`` method.

* Private :class:`~django.db.models.FileField` methods ``get_directory_name()``
  and ``get_filename()`` are no longer called (and are now deprecated) which is
  a backwards incompatible change for users overriding those methods on custom
  fields. To adapt such code, override ``FileField.generate_filename()`` or
  :meth:`Storage.generate_filename()
  <django.core.files.storage.Storage.generate_filename>` instead. It
  might be possible to use :attr:`~django.db.models.FileField.upload_to` also.

* The subject of mail sent by ``AdminEmailHandler`` is no longer truncated at
  989 characters. If you were counting on a limited length, truncate the subject
  yourself.

* Private expressions ``django.db.models.expressions.Date`` and ``DateTime``
  are removed. The new :class:`~django.db.models.functions.datetime.Trunc`
  expressions provide the same functionality.

* The ``_base_manager`` and ``_default_manager`` attributes are removed from
  model instances. They remain accessible on the model class.

* Accessing a deleted field on a model instance, e.g. after ``del obj.field``,
  reloads the field's value instead of raising ``AttributeError``.

* If you subclass ``AbstractBaseUser`` and override ``clean()``, be sure it
  calls ``super()``. :meth:`.AbstractBaseUser.normalize_username` is called in
  a new :meth:`.AbstractBaseUser.clean` method.

* Private API ``django.forms.models.model_to_dict()`` returns a queryset rather
  than a list of primary keys for ``ManyToManyField``\s .

.. _deprecated-features-1.10:

Features deprecated in 1.10
===========================

Direct assignment to a reverse foreign key or many-to-many relation
-------------------------------------------------------------------

Instead of assigning related objects using direct assignment::

    >>> new_list = [obj1, obj2, obj3]
    >>> e.related_set = new_list

Use the :meth:`~django.db.models.fields.related.RelatedManager.set` method
added in Django 1.9::

        >>> e.related_set.set([obj1, obj2, obj3])

This prevents confusion about an assignment resulting in an implicit save.

Non-timezone-aware :class:`~django.core.files.storage.Storage` API
------------------------------------------------------------------

The old, non-timezone-aware methods ``accessed_time()``, ``created_time()``,
and ``modified_time()`` are deprecated in favor of the new ``get_*_time()``
methods.

Third-party storage backends should implement the new methods and mark the old
ones as deprecated. Until then, the new ``get_*_time()`` methods on the base
:class:`~django.core.files.storage.Storage` class convert ``datetime``\s from
the old methods as required and emit a deprecation warning as they do so.

Third-party storage backends may retain the old methods as long as they
wish to support earlier versions of Django.

:mod:`django.contrib.gis`
-------------------------

* The ``get_srid()`` and ``set_srid()`` methods of
  :class:`~django.contrib.gis.geos.GEOSGeometry` are deprecated in favor
  of the :attr:`~django.contrib.gis.geos.GEOSGeometry.srid` property.

* The ``get_x()``, ``set_x()``, ``get_y()``, ``set_y()``, ``get_z()``, and
  ``set_z()`` methods of :class:`~django.contrib.gis.geos.Point` are deprecated
  in favor of the ``x``, ``y``, and ``z`` properties.

* The ``get_coords()`` and ``set_coords()`` methods of
  :class:`~django.contrib.gis.geos.Point` are deprecated in favor of the
  ``tuple`` property.

* The ``cascaded_union`` property of
  :class:`~django.contrib.gis.geos.MultiPolygon` is deprecated in favor of the
  :attr:`~django.contrib.gis.geos.GEOSGeometry.unary_union` property.

* The ``django.contrib.gis.utils.precision_wkt()`` function is deprecated in
  favor of :class:`~django.contrib.gis.geos.WKTWriter`.

``CommaSeparatedIntegerField`` model field
------------------------------------------

``CommaSeparatedIntegerField`` is deprecated in favor of
:class:`~django.db.models.CharField` with the
:func:`~django.core.validators.validate_comma_separated_integer_list`
validator::

    from django.core.validators import validate_comma_separated_integer_list
    from django.db import models

    class MyModel(models.Model):
        numbers = models.CharField(..., validators=[validate_comma_separated_integer_list])

If you're using Oracle, ``CharField`` uses a different database field  type
(``NVARCHAR2``) than ``CommaSeparatedIntegerField`` (``VARCHAR2``). Depending
on your database settings, this might imply a different encoding, and thus a
different length (in bytes) for the same contents. If your stored values are
longer than the 4000 byte limit of ``NVARCHAR2``, you should use ``TextField``
(``NCLOB``) instead. In this case, if you have any queries that group by the
field (e.g. annotating the model with an aggregation or using ``distinct()``)
you'll need to change them (to defer the field).

Using a model name as a query lookup when ``default_related_name`` is set
-------------------------------------------------------------------------

Assume the following models::

    from django.db import models

    class Foo(models.Model):
        pass

    class Bar(models.Model):
        foo = models.ForeignKey(Foo)

        class Meta:
            default_related_name = 'bars'

In older versions, :attr:`~django.db.models.Options.default_related_name`
couldn't be used as a query lookup. This is fixed and support for the old
lookup name is deprecated. For example, since ``default_related_name`` is set
in model ``Bar``, instead of using the model name ``bar`` as the lookup::

    >>> bar = Bar.objects.get(pk=1)
    >>> Foo.objects.get(bar=bar)

use the default_related_name ``bars``::

    >>> Foo.objects.get(bars=bar)

.. _search-lookup-replacement:

``__search`` query lookup
-------------------------

The ``search`` lookup, which supports MySQL only and is extremely limited in
features, is deprecated. Replace it with a custom lookup::

    from django.db import models

    class Search(models.Lookup):
        lookup_name = 'search'

        def as_mysql(self, compiler, connection):
            lhs, lhs_params = self.process_lhs(compiler, connection)
            rhs, rhs_params = self.process_rhs(compiler, connection)
            params = lhs_params + rhs_params
            return 'MATCH (%s) AGAINST (%s IN BOOLEAN MODE)' % (lhs, rhs), params

    models.CharField.register_lookup(Search)
    models.TextField.register_lookup(Search)

.. _user-is-auth-anon-deprecation:

Using ``User.is_authenticated()`` and ``User.is_anonymous()`` as methods
------------------------------------------------------------------------

The ``is_authenticated()`` and ``is_anonymous()`` methods of
:class:`~django.contrib.auth.models.AbstractBaseUser` and
:class:`~django.contrib.auth.models.AnonymousUser` classes are now
properties. They will still work as methods until Django 2.0, but all usage
in Django now uses attribute access.

For example, if you use
:class:`~django.contrib.auth.middleware.AuthenticationMiddleware` and want
to know whether the user is currently logged-in you would use::

    if request.user.is_authenticated:
        ... # Do something for logged-in users.
    else:
        ... # Do something for anonymous users.

instead of ``request.user.is_authenticated()``.

This change avoids accidental information leakage if you forget to call the
method, e.g.::

    if request.user.is_authenticated:
        return sensitive_information

If you override these methods in a custom user model, you must change them to
properties or attributes.

Django uses a ``CallableBool`` object to allow these attributes to work as both
a property and a method. Thus, until the deprecation period ends, you cannot
compare these properties using the ``is`` operator. That is, the following
won't work::

    if request.user.is_authenticated is True:
        ...

Custom manager classes available through ``prefetch_related`` must define a ``_apply_rel_filters()`` method
-----------------------------------------------------------------------------------------------------------

If you defined a custom manager class available through
:meth:`~django.db.models.query.QuerySet.prefetch_related` you must make sure
it defines a ``_apply_rel_filters()`` method.

This method must accept a :class:`~django.db.models.query.QuerySet` instance
as its single argument and return a filtered version of the queryset for the
model instance the manager is bound to.

The "escape" half of ``django.utils.safestring``
------------------------------------------------

The ``mark_for_escaping()`` function and the classes it uses: ``EscapeData``,
``EscapeBytes``, ``EscapeText``, ``EscapeString``, and ``EscapeUnicode`` are
deprecated.

As a result, the "lazy" behavior of the ``escape`` filter (where it would
always be applied as the last filter no matter where in the filter chain it
appeared) is deprecated. The filter will change to immediately apply
:func:`~django.utils.html.conditional_escape` in Django 2.0.

``Manager.use_for_related_fields`` and inheritance changes
----------------------------------------------------------

``Manager.use_for_related_fields`` is deprecated in favor of setting
:attr:`Meta.base_manager_name <django.db.models.Options.base_manager_name>` on
the model.

Model ``Manager`` inheritance will follow MRO inheritance rules in Django 2.0,
changing the current behavior where managers defined on non-abstract base
classes aren't inherited by child classes. A deprecating warning with
instructions on how to adapt your code is raised if you have any affected
managers. You'll either redeclare a manager from an abstract model on the child
class to override the manager from the concrete model, or you'll set the
model's ``Meta.manager_inheritance_from_future=True`` option to opt-in to the
new inheritance behavior.

During the deprecation period, ``use_for_related_fields`` will be honored and
raise a warning, even if a ``base_manager_name`` is set. This allows
third-party code to preserve legacy behavior while transitioning to the new
API. The warning can be silenced by setting
``silence_use_for_related_fields_deprecation=True`` on the manager.

Miscellaneous
-------------

* The ``makemigrations --exit`` option is deprecated in favor of the
  :option:`makemigrations --check` option.

* ``django.utils.functional.allow_lazy()`` is deprecated in favor of the new
  :func:`~django.utils.functional.keep_lazy` function which can be used with a
  more natural decorator syntax.

* The ``shell --plain`` option is deprecated in favor of ``-i python`` or
  ``--interface python``.

* Importing from the ``django.core.urlresolvers`` module is deprecated in
  favor of its new location, :mod:`django.urls`.

* The template ``Context.has_key()`` method is deprecated in favor of ``in``.

* The private attribute ``virtual_fields`` of ``Model._meta`` is
  deprecated in favor of ``private_fields``.

* The private keyword arguments ``virtual_only`` in
  ``Field.contribute_to_class()`` and ``virtual`` in
  ``Model._meta.add_field()`` are deprecated in favor of ``private_only``
  and ``private``, respectively.

* The ``javascript_catalog()`` and ``json_catalog()`` views are deprecated in
  favor of class-based views :class:`~django.views.i18n.JavaScriptCatalog`
  and :class:`~django.views.i18n.JSONCatalog`.

* In multi-table inheritance, implicit promotion of a ``OneToOneField`` to a
  ``parent_link`` is deprecated. Add ``parent_link=True`` to such fields.

* The private API ``Widget._format_value()`` is made public and renamed to
  :meth:`~django.forms.Widget.format_value`. The old name will work
  through a deprecation period.

* Private ``FileField`` methods ``get_directory_name()`` and ``get_filename()``
  are deprecated in favor of performing this work in
  :meth:`Storage.generate_filename()
  <django.core.files.storage.Storage.generate_filename>`).

* Old-style middleware that uses  ``settings.MIDDLEWARE_CLASSES`` are
  deprecated. :ref:`Adapt old, custom middleware <upgrading-middleware>` and
  use the new :setting:`MIDDLEWARE` setting.

.. _removed-features-1.10:

Features removed in 1.10
========================

These features have reached the end of their deprecation cycle and are removed
in Django 1.10. See :ref:`deprecated-features-1.8` for details, including how
to remove usage of these features.

* Support for calling a ``SQLCompiler`` directly as an alias for calling its
  ``quote_name_unless_alias`` method is removed.

* The ``cycle`` and ``firstof`` template tags are removed from the ``future``
  template tag library.

* ``django.conf.urls.patterns()`` is removed.

* Support for the ``prefix`` argument to
  ``django.conf.urls.i18n.i18n_patterns()`` is removed.

* ``SimpleTestCase.urls`` is removed.

* Using an incorrect count of unpacked values in the ``for`` template tag
  raises an exception rather than failing silently.

* The ability to :func:`~django.urls.reverse` URLs using a dotted Python path
  is removed.

* The ability to use a dotted Python path for the ``LOGIN_URL`` and
  ``LOGIN_REDIRECT_URL`` settings is removed.

* Support for ``optparse`` is dropped for custom management commands.

* The class ``django.core.management.NoArgsCommand`` is removed.

* ``django.core.context_processors`` module is removed.

* ``django.db.models.sql.aggregates`` module is removed.

* ``django.contrib.gis.db.models.sql.aggregates`` module is removed.

* The following methods and properties of ``django.db.sql.query.Query`` are
  removed:

  * Properties: ``aggregates`` and ``aggregate_select``
  * Methods: ``add_aggregate``, ``set_aggregate_mask``, and
    ``append_aggregate_mask``.

* ``django.template.resolve_variable`` is removed.

* The following private APIs are removed from
  :class:`django.db.models.options.Options` (``Model._meta``):

  * ``get_field_by_name()``
  * ``get_all_field_names()``
  * ``get_fields_with_model()``
  * ``get_concrete_fields_with_model()``
  * ``get_m2m_with_model()``
  * ``get_all_related_objects()``
  * ``get_all_related_objects_with_model()``
  * ``get_all_related_many_to_many_objects()``
  * ``get_all_related_m2m_objects_with_model()``

* The ``error_message`` argument of ``django.forms.RegexField`` is removed.

* The ``unordered_list`` filter no longer supports old style lists.

* Support for string ``view`` arguments to ``url()`` is removed.

* The backward compatible shim  to rename ``django.forms.Form._has_changed()``
  to ``has_changed()`` is removed.

* The ``removetags`` template filter is removed.

* The ``remove_tags()`` and ``strip_entities()`` functions in
  ``django.utils.html`` is removed.

* The ``is_admin_site`` argument to
  ``django.contrib.auth.views.password_reset()`` is removed.

* ``django.db.models.field.subclassing.SubfieldBase`` is removed.

* ``django.utils.checksums`` is removed.

* The ``original_content_type_id`` attribute on
  ``django.contrib.admin.helpers.InlineAdminForm`` is removed.

* The backwards compatibility shim to allow ``FormMixin.get_form()`` to be
  defined with no default value for its ``form_class`` argument is removed.

* The following settings are removed, and :doc:`you must upgrade
  </ref/templates/upgrading>` to the :setting:`TEMPLATES` setting:

  * ``ALLOWED_INCLUDE_ROOTS``
  * ``TEMPLATE_CONTEXT_PROCESSORS``
  * ``TEMPLATE_DEBUG``
  * ``TEMPLATE_DIRS``
  * ``TEMPLATE_LOADERS``
  * ``TEMPLATE_STRING_IF_INVALID``

* The backwards compatibility alias ``django.template.loader.BaseLoader`` is
  removed.

* Django template objects returned by
  :func:`~django.template.loader.get_template` and
  :func:`~django.template.loader.select_template` no longer accept a
  :class:`~django.template.Context` in their
  :meth:`~django.template.backends.base.Template.render()` method.

* :doc:`Template response APIs </ref/template-response>` enforce the use of
  :class:`dict` and backend-dependent template objects instead of
  :class:`~django.template.Context` and :class:`~django.template.Template`
  respectively.

* The ``current_app`` parameter for the following function and classes is
  removed:

  * ``django.shortcuts.render()``
  * ``django.template.Context()``
  * ``django.template.RequestContext()``
  * ``django.template.response.TemplateResponse()``

* The ``dictionary`` and ``context_instance`` parameters for the following
  functions are removed:

  * ``django.shortcuts.render()``
  * ``django.shortcuts.render_to_response()``
  * ``django.template.loader.render_to_string()``

* The ``dirs`` parameter for the following functions is removed:

  * ``django.template.loader.get_template()``
  * ``django.template.loader.select_template()``
  * ``django.shortcuts.render()``
  * ``django.shortcuts.render_to_response()``

* Session verification is enabled regardless of whether or not
  ``'django.contrib.auth.middleware.SessionAuthenticationMiddleware'`` is in
  ``MIDDLEWARE_CLASSES``. ``SessionAuthenticationMiddleware`` no longer has
  any purpose and can be removed from ``MIDDLEWARE_CLASSES``. It's kept as
  a stub until Django 2.0 as a courtesy for users who don't read this note.

* Private attribute ``django.db.models.Field.related`` is removed.

* The ``--list`` option of the ``migrate`` management command is removed.

* The ``ssi`` template tag is removed.

* Support for the ``=`` comparison operator in the ``if`` template tag is
  removed.

* The backwards compatibility shims to allow ``Storage.get_available_name()``
  and ``Storage.save()`` to be defined without a ``max_length`` argument are
  removed.

* Support for the legacy ``%(<foo>)s`` syntax in ``ModelFormMixin.success_url``
  is removed.

* ``GeoQuerySet`` aggregate methods ``collect()``, ``extent()``, ``extent3d()``,
  ``make_line()``, and ``unionagg()`` are removed.

* The ability to specify ``ContentType.name`` when creating a content type
  instance is removed.

* Support for the old signature of ``allow_migrate`` is removed.

* Support for the syntax of ``{% cycle %}`` that uses comma-separated arguments
  is removed.

* The warning that :class:`~django.core.signing.Signer` issued when given an
  invalid separator is now a ``ValueError``.
