Moved the AUTH_USER_MODEL setting changed receiver.

Test suites besides Django's may need the same behavior.

django/test/signals.py

@@ -3,6 +3,7 @@ import threading
 import time
 import warnings
 
+from django.apps import apps
 from django.core.signals import setting_changed
 from django.db import connections, router
 from django.db.utils import ConnectionRouter
@@ -168,3 +169,9 @@ def auth_password_validators_changed(**kwargs):
     if kwargs['setting'] == 'AUTH_PASSWORD_VALIDATORS':
         from django.contrib.auth.password_validation import get_default_password_validators
         get_default_password_validators.cache_clear()
+
+
+@receiver(setting_changed)
+def user_model_swapped(**kwargs):
+    if kwargs['setting'] == 'AUTH_USER_MODEL':
+        apps.clear_cache()

tests/auth_tests/test_basic.py

@@ -3,25 +3,16 @@ from __future__ import unicode_literals
 
 import warnings
 
-from django.apps import apps
 from django.contrib.auth import get_user_model
 from django.contrib.auth.models import AnonymousUser, User
 from django.core.exceptions import ImproperlyConfigured
 from django.db import IntegrityError
-from django.dispatch import receiver
 from django.test import TestCase, override_settings
-from django.test.signals import setting_changed
 from django.utils import translation
 
 from .models import CustomUser
 
 
-@receiver(setting_changed)
-def user_model_swapped(**kwargs):
-    if kwargs['setting'] == 'AUTH_USER_MODEL':
-        apps.clear_cache()
-
-
 class BasicTestCase(TestCase):
     def test_user(self):
         "Check that users can be created and can set their password"