  from django.contrib.auth import BACKEND_SESSION_KEY, authenticate, get_user
  from django.contrib.auth.backends import ModelBackend
  from django.contrib.auth.hashers import MD5PasswordHasher
  from django.contrib.auth.models import AnonymousUser, Group, Permission, User
  from django.contrib.auth.tests.custom_user import (
      CustomPermissionsUser, CustomUser, ExtensionUser,
  )
  from django.contrib.contenttypes.models import ContentType
  from django.core.exceptions import ImproperlyConfigured, PermissionDenied
  from django.http import HttpRequest
  from django.test import TestCase, modify_settings, override_settings
  
 
</s> remove # Needed so model is installed when tests are run independently:
from django.contrib.auth.tests.custom_user import IsActiveTestUser1  # NOQA
 </s> add  </s> remove from django.contrib.auth.tests.custom_user import (
    CustomUser, CustomUserBadRequiredFields, CustomUserNonListRequiredFields,
    CustomUserNonUniqueUsername, CustomUserWithFK, Email,
)
 </s> add from django.contrib.auth.tests.custom_user import CustomUser </s> remove # Needed so model is installed when tests are run independently:
from django.contrib.auth.tests.custom_user import CustomUser  # NOQA
 </s> add 
from django.contrib.auth.tests.custom_user import CustomUser, ExtensionUser
  from django.contrib.auth import BACKEND_SESSION_KEY, authenticate, get_user
  from django.contrib.auth.backends import ModelBackend
  from django.contrib.auth.hashers import MD5PasswordHasher
  from django.contrib.auth.models import AnonymousUser, Group, Permission, User
from django.contrib.auth.tests.custom_user import CustomUser, ExtensionUser
from django.contrib.auth.tests.custom_user import CustomUser, ExtensionUser
from django.contrib.auth.tests.custom_user import CustomUser, ExtensionUser
  from django.contrib.contenttypes.models import ContentType
  from django.core.exceptions import ImproperlyConfigured, PermissionDenied
  from django.http import HttpRequest
  from django.test import TestCase, modify_settings, override_settings
  
keep keep keep keep replace replace replace keep keep keep keep keep
 Moved non-documented auth test models to the new test location. 
tests/auth_tests/test_auth_backends.py