Moved the AUTH_USER_MODEL setting changed receiver.

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

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"