[1.7.x] Fixed #22653 -- Added some database feature flags to tests.

Thanks Rahul Priyadarshi.

Backport of 99f5ea9c from master

tests/admin_views/tests.py

@@ -28,7 +28,7 @@ from django.contrib.auth.models import Group, User, Permission
 from django.contrib.contenttypes.models import ContentType
 from django.forms.utils import ErrorList
 from django.template.response import TemplateResponse
-from django.test import TestCase
+from django.test import TestCase, skipUnlessDBFeature
 from django.test.utils import patch_logger
 from django.test import override_settings
 from django.utils import formats
@@ -1527,6 +1527,7 @@ class AdminViewsNoUrlTest(TestCase):
         self.client.get('/test_admin/admin/logout/')
 
 
+@skipUnlessDBFeature('can_defer_constraint_checks')
 @override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))
 class AdminViewDeletedObjectsTest(TestCase):
     urls = "admin_views.urls"

tests/fixtures_regress/tests.py

@@ -405,6 +405,7 @@ class TestFixtures(TestCase):
             % widget.pk
         )
 
+    @skipUnlessDBFeature('supports_forward_references')
     def test_loaddata_works_when_fixture_has_forward_refs(self):
         """
         Regression for #3615 - Forward references cause fixtures not to load in MySQL (InnoDB)
@@ -429,6 +430,7 @@ class TestFixtures(TestCase):
                 verbosity=0,
             )
 
+    @skipUnlessDBFeature('supports_forward_references')
     @override_settings(FIXTURE_DIRS=[os.path.join(_cur_dir, 'fixtures_1'),
                                      os.path.join(_cur_dir, 'fixtures_2')])
     def test_loaddata_forward_refs_split_fixtures(self):

tests/serializers/tests.py

@@ -16,7 +16,7 @@ except ImportError:
 
 from django.core import management, serializers
 from django.db import transaction, connection
-from django.test import TestCase, TransactionTestCase, override_settings
+from django.test import TestCase, TransactionTestCase, override_settings, skipUnlessDBFeature
 from django.test.utils import Approximate
 from django.utils import six
 from django.utils.six import StringIO
@@ -267,6 +267,7 @@ class SerializersTransactionTestBase(object):
 
     available_apps = ['serializers']
 
+    @skipUnlessDBFeature('supports_forward_references')
     def test_forward_refs(self):
         """
         Tests that objects ids can be referenced before they are

tests/serializers_regress/tests.py

@@ -402,6 +402,7 @@ if connection.features.allows_auto_pk_0:
 # registered serializers are automatically tested.
 
 
+@skipUnlessDBFeature('can_defer_constraint_checks')
 class SerializerTests(TestCase):
     def test_get_unknown_serializer(self):
         """