tests: add get_or_create

Ran the various component tests in get_or_create,
filed and grouped tests that fail due to lack of savepoints
in Cloud Spanner, following Tim's advisory in #384.

Fixes #270
Fixes #384

.travis.yml

@@ -26,7 +26,7 @@ env:
         - DJANGO_TEST_APPS="expressions expressions_window"
         - DJANGO_TEST_APPS="field_defaults field_subclassing file_storage file_uploads"
         - DJANGO_TEST_APPS="fixtures fixtures_model_package from_db_value"
-        - DJANGO_TEST_APPS="get_earliest_or_latest get_object_or_404"
+        - DJANGO_TEST_APPS="get_earliest_or_latest get_object_or_404 get_or_create"
         - DJANGO_TEST_APPS="i18n"
         - DJANGO_TEST_APPS="indexes inline_formsets introspection invalid_models_tests"
         - DJANGO_TEST_APPS="known_related_objects lookup max_lengths m2m_and_m2o m2m_intermediary m2m_multiple"

django_spanner/features.py

@@ -198,8 +198,16 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         'cache.tests.CreateCacheTableForDBCacheTests',
         'cache.tests.DBCacheTests',
         'cache.tests.DBCacheWithTimeZoneTests',
-        # A rollback failed and should be investigated:
+        # Tests that require savepoints.
         # https://github.com/orijtech/django-spanner/issues/299
+        'get_or_create.tests.GetOrCreateTests.test_get_or_create_invalid_params',
+        'get_or_create.tests.GetOrCreateTestsWithManualPKs.test_create_with_duplicate_primary_key',
+        'get_or_create.tests.GetOrCreateTestsWithManualPKs.test_get_or_create_raises_IntegrityError_plus_traceback', # noqa
+        'get_or_create.tests.GetOrCreateTestsWithManualPKs.test_savepoint_rollback',
+        'get_or_create.tests.GetOrCreateThroughManyToMany.test_something',
+        'get_or_create.tests.UpdateOrCreateTests.test_integrity',
+        'get_or_create.tests.UpdateOrCreateTests.test_manual_primary_key_test',
+        'get_or_create.tests.UpdateOrCreateTestsWithManualPKs.test_create_with_duplicate_primary_key',
         'test_utils.tests.TestBadSetUpTestData.test_failure_in_setUpTestData_should_rollback_transaction',
         # Spanner doesn't support views.
         'inspectdb.tests.InspectDBTransactionalTests.test_include_views',