          "user is not authenticated after a backend raises permission denied #2550"
          self.assertEqual(authenticate(username='test', password='test'), None)
  
      @override_settings(AUTHENTICATION_BACKENDS=tuple(
              settings.AUTHENTICATION_BACKENDS) + (backend, ))
      def test_authenticates(self):
          self.assertEqual(authenticate(username='test', password='test'), self.user1)
  
  
  class NewModelBackend(ModelBackend):
 
</s> remove for format in [
            f for f in serializers.get_serializer_formats()
            if not isinstance(serializers.get_serializer(f), serializers.BadSerializer)
]:
 </s> add for format in [f for f in serializers.get_serializer_formats()
               if not isinstance(serializers.get_serializer(f), serializers.BadSerializer)]: </s> remove                 data={'description': 'And a final one'},
                files={'image': SimpleUploadedFile('test3.png', image_data)}, instance=instance)
 </s> add             data={'description': 'And a final one'},
            files={'image': SimpleUploadedFile('test3.png', image_data)}, instance=instance) </s> remove                 request.path_info, supported=self._supported_languages
 </s> add             request.path_info, supported=self._supported_languages </s> remove                         form[cl.model._meta.pk.name].is_hidden)):
 </s> add                     form[cl.model._meta.pk.name].is_hidden)): </s> remove         return "PK = %d, base_name = %s, derived_name = %s" \
                % (self.customPK, self.base_name, self.derived_name)
 </s> add         return "PK = %d, base_name = %s, derived_name = %s" % (
            self.customPK, self.base_name, self.derived_name)
        settings.AUTHENTICATION_BACKENDS) + (backend, ))
          "user is not authenticated after a backend raises permission denied #2550"
          self.assertEqual(authenticate(username='test', password='test'), None)
  
      @override_settings(AUTHENTICATION_BACKENDS=tuple(
        settings.AUTHENTICATION_BACKENDS) + (backend, ))
      def test_authenticates(self):
          self.assertEqual(authenticate(username='test', password='test'), self.user1)
  
  
  class NewModelBackend(ModelBackend):
keep keep keep keep replace keep keep keep keep keep
 Fixed #21288 -- Fixed E126 pep8 warnings 
django/contrib/auth/tests/test_auth_backends.py