Fixed #24116 -- Moved AdminSite.check_dependencies() to system checks.

django/contrib/admin/apps.py

 from django.apps import AppConfig
-from django.contrib.admin.checks import check_admin_app
+from django.contrib.admin.checks import check_admin_app, check_dependencies
 from django.core import checks
 from django.utils.translation import ugettext_lazy as _
 
@@ -11,6 +11,7 @@ class SimpleAdminConfig(AppConfig):
     verbose_name = _("Administration")
 
     def ready(self):
+        checks.register(check_dependencies, checks.Tags.admin)
         checks.register(check_admin_app, checks.Tags.admin)
 
 

django/contrib/admin/checks.py

@@ -3,6 +3,8 @@ from __future__ import unicode_literals
 
 from itertools import chain
 
+from django.apps import apps
+from django.conf import settings
 from django.contrib.admin.utils import (
     NotRelationField, flatten, get_fields_from_path,
 )
@@ -12,6 +14,7 @@ from django.db import models
 from django.forms.models import (
     BaseModelForm, BaseModelFormSet, _get_foreign_key,
 )
+from django.template.engine import Engine
 
 
 def check_admin_app(**kwargs):
@@ -20,6 +23,46 @@ def check_admin_app(**kwargs):
     return system_check_errors
 
 
+def check_dependencies(**kwargs):
+    """
+    Check that the admin's dependencies are correctly installed.
+    """
+    errors = []
+    # contrib.contenttypes must be installed.
+    if not apps.is_installed('django.contrib.contenttypes'):
+        missing_app = checks.Error(
+            "'django.contrib.contenttypes' must be in INSTALLED_APPS in order "
+            "to use the admin application.",
+            id="admin.E401",
+        )
+        errors.append(missing_app)
+    # The auth context processor must be installed if using the default
+    # authentication backend.
+    try:
+        default_template_engine = Engine.get_default()
+    except Exception:
+        # Skip this non-critical check:
+        # 1. if the user has a non-trivial TEMPLATES setting and Django
+        #    can't find a default template engine
+        # 2. if anything goes wrong while loading template engines, in
+        #    order to avoid raising an exception from a confusing location
+        # Catching ImproperlyConfigured suffices for 1. but 2. requires
+        # catching all exceptions.
+        pass
+    else:
+        if ('django.contrib.auth.context_processors.auth'
+                not in default_template_engine.context_processors
+                and 'django.contrib.auth.backends.ModelBackend'
+                in settings.AUTHENTICATION_BACKENDS):
+            missing_template = checks.Error(
+                "'django.contrib.auth.context_processors.auth' must be in "
+                "TEMPLATES in order to use the admin application.",
+                id="admin.E402"
+                )
+            errors.append(missing_template)
+    return errors
+
+
 class BaseModelAdminChecks(object):
 
     def check(self, admin_obj, **kwargs):

django/contrib/admin/sites.py

@@ -7,7 +7,6 @@ from django.contrib.auth import REDIRECT_FIELD_NAME
 from django.core.exceptions import ImproperlyConfigured, PermissionDenied
 from django.db.models.base import ModelBase
 from django.http import Http404, HttpResponseRedirect
-from django.template.engine import Engine
 from django.template.response import TemplateResponse
 from django.urls import NoReverseMatch, reverse
 from django.utils import six
@@ -172,40 +171,6 @@ class AdminSite(object):
         """
         return request.user.is_active and request.user.is_staff
 
-    def check_dependencies(self):
-        """
-        Check that all things needed to run the admin have been correctly installed.
-
-        The default implementation checks that admin and contenttypes apps are
-        installed, as well as the auth context processor.
-        """
-        if not apps.is_installed('django.contrib.admin'):
-            raise ImproperlyConfigured(
-                "Put 'django.contrib.admin' in your INSTALLED_APPS "
-                "setting in order to use the admin application.")
-        if not apps.is_installed('django.contrib.contenttypes'):
-            raise ImproperlyConfigured(
-                "Put 'django.contrib.contenttypes' in your INSTALLED_APPS "
-                "setting in order to use the admin application.")
-        try:
-            default_template_engine = Engine.get_default()
-        except Exception:
-            # Skip this non-critical check:
-            # 1. if the user has a non-trivial TEMPLATES setting and Django
-            #    can't find a default template engine
-            # 2. if anything goes wrong while loading template engines, in
-            #    order to avoid raising an exception from a confusing location
-            # Catching ImproperlyConfigured suffices for 1. but 2. requires
-            # catching all exceptions.
-            pass
-        else:
-            if ('django.contrib.auth.context_processors.auth'
-                    not in default_template_engine.context_processors):
-                raise ImproperlyConfigured(
-                    "Enable 'django.contrib.auth.context_processors.auth' "
-                    "in your TEMPLATES setting in order to use the admin "
-                    "application.")
-
     def admin_view(self, view, cacheable=False):
         """
         Decorator to create an admin view attached to this ``AdminSite``. This
@@ -257,9 +222,6 @@ class AdminSite(object):
         # and django.contrib.contenttypes.views imports ContentType.
         from django.contrib.contenttypes import views as contenttype_views
 
-        if settings.DEBUG:
-            self.check_dependencies()
-
         def wrap(view, cacheable=False):
             def wrapper(*args, **kwargs):
                 return self.admin_view(view, cacheable)(*args, **kwargs)

docs/ref/checks.txt

@@ -409,6 +409,16 @@ registered as an inline on a :class:`~django.contrib.admin.ModelAdmin`.
 * **admin.E304**: ``<model>`` has no ``GenericForeignKey`` using content type
   field ``<field name>`` and object ID field ``<field name>``.
 
+AdminSite
+~~~~~~~~~
+
+The following checks are performed on the default
+:class:`~django.contrib.admin.AdminSite`:
+
+* **admin.E401**: :mod:`django.contrib.contenttypes` must be in
+  :setting:`INSTALLED_APPS` in order to use the admin application.
+* **admin.E402**: :mod:`django.contrib.auth.context_processors.auth`
+  must be in :setting:`TEMPLATES` in order to use the admin application.
 
 Auth
 ----

tests/admin_checks/tests.py

@@ -54,6 +54,44 @@ class SystemChecksTestCase(SimpleTestCase):
             admin.site.unregister(Song)
             admin.sites.system_check_errors = []
 
+    @override_settings(INSTALLED_APPS=['django.contrib.admin'])
+    def test_contenttypes_dependency(self):
+        errors = admin.checks.check_dependencies()
+        expected = [
+            checks.Error(
+                "'django.contrib.contenttypes' must be in "
+                "INSTALLED_APPS in order to use the admin application.",
+                id="admin.E401",
+            )
+        ]
+        self.assertEqual(errors, expected)
+
+    @override_settings(
+        INSTALLED_APPS=[
+            'django.contrib.admin',
+            'django.contrib.auth',
+            'django.contrib.contenttypes',
+        ],
+        TEMPLATES=[{
+            'BACKEND': 'django.template.backends.django.DjangoTemplates',
+            'DIRS': [],
+            'APP_DIRS': True,
+            'OPTIONS': {
+                'context_processors': [],
+            },
+        }],
+    )
+    def test_auth_contextprocessor_dependency(self):
+        errors = admin.checks.check_dependencies()
+        expected = [
+            checks.Error(
+                "'django.contrib.auth.context_processors.auth' must be in "
+                "TEMPLATES in order to use the admin application.",
+                id="admin.E402",
+            )
+        ]
+        self.assertEqual(errors, expected)
+
     @override_settings(DEBUG=True)
     def test_custom_adminsite(self):
         class CustomAdminSite(admin.AdminSite):