https://groups.google.com/d/msg/django-developers/dyldP9kFADc/rHTlRBVEP8MJ

Thanks Shai Berger for the report.

This commit also adds tests for the redirect feature of most auth views.
It also cleans up the tests, most notably using @override_settings instead
of ad-hoc setUp/tearDown methods.

Thanks to caumons for the report.

Conflicts:
	docs/releases/1.6.txt

Fixed #20442: NoneType error when fetching a stale ContentType with get_for_id

Add needed Imports to the Documentation, Part II

Integrity problems when using get_or_create through M2M

Fixes #18896. Add tests verifying that you can get IntegrityErrors using get_or_create through relations like M2M, and it also adds a note into the documentation warning about it

Fixed #19070 -- Additional test for urlize and brackets

Fixed #11442 -- Postgresql backend casts all inet types to text

Add missing imports and models to the examples in internationalization and localization documentation

Fixed #20126 -- XViewMiddleware moved to django.contrib.admindocs.middleware

Fixed #20340 - document required return value for disable_constraint_checking

Fixed #11915: generic Accept-Language matches country-specific variants

Fixed #11160: Formset non_form_errors returns ErrorList() if is_valid is not called

Fixed #18990: Loaddata now complains if fixture doesn't exist

Moved admin validation code to classes and have those be class
attributes to the ModelAdmin classes.

Added example of using sitemaps with static views.

Added TransRealMixin to fix i18n global state pollution in the test suite

If the fixture doesn't exist, loaddata will output a warning.

The fixture named "initial_data" is exceptional though; if it
doesn't exist, the warning is not emitted. This allows syncdb and
flush management commands to attempt to load it without causing
spurious warnings.

Thanks to Derega, ptone, dirigeant and d1ffuz0r for contributions
to the ticket.

Note the don't require sessions to be in installed apps.

Fixed #20454: Make Urdu (ur) recognized as RTL language

Fixed #20233 - Full custom user model example isn't really full

The fixture named "initial_data" is exceptional though; if it
doesn't exist, the error is not raised. This allows syncdb and
flush management commands to attempt to load it without causing
an error if it doesn't exist.

A simple docstring to clarify a part of the code that might be confusing to understand