tests: Remove use of 'oslo_db.sqlalchemy.test_base'

The various test cases and mixins in 'oslo_db.sqlalchemy.test_base' have
been deprecated since oslo.db 4.34.0 (March 2018). Remove use of these.

Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
Change-Id: I67eff8c9733500813435cde2dbda28a3c4a3ccf3

manila/tests/db/migrations/alembic/test_migration.py

@@ -20,9 +20,11 @@ Tests for database migrations.
 from unittest import mock
 
 from alembic import script
-from oslo_db.sqlalchemy import test_base
+from oslo_db.sqlalchemy import enginefacade
+from oslo_db.sqlalchemy import test_fixtures
 from oslo_db.sqlalchemy import test_migrations
 from oslo_log import log
+from oslotest import base as test_base
 from sqlalchemy.sql import text
 
 from manila.db.migrations.alembic import migration
@@ -36,6 +38,10 @@ class ManilaMigrationsCheckers(test_migrations.WalkVersionsMixin,
                                migrations_data_checks.DbMigrationsData):
     """Test alembic migrations."""
 
+    def setUp(self):
+        super().setUp()
+        self.engine = enginefacade.writer.get_engine()
+
     @property
     def snake_walk(self):
         return True
@@ -168,9 +174,13 @@ class ManilaMigrationsCheckers(test_migrations.WalkVersionsMixin,
                          "Db migrations should have only one branch.")
 
 
-class TestManilaMigrationsMySQL(ManilaMigrationsCheckers,
-                                test_base.MySQLOpportunisticTestCase):
+class TestManilaMigrationsMySQL(
+    ManilaMigrationsCheckers,
+    test_fixtures.OpportunisticDBTestMixin,
+    test_base.BaseTestCase,
+):
     """Run migration tests on MySQL backend."""
+    FIXTURE = test_fixtures.MySQLOpportunisticFixture
 
     @test_utils.set_timeout(300)
     def test_mysql_innodb(self):
@@ -204,5 +214,9 @@ class TestManilaMigrationsMySQL(ManilaMigrationsCheckers,
 
 
 class TestManilaMigrationsPostgreSQL(
-        ManilaMigrationsCheckers, test_base.PostgreSQLOpportunisticTestCase):
+    ManilaMigrationsCheckers,
+    test_fixtures.OpportunisticDBTestMixin,
+    test_base.BaseTestCase,
+):
     """Run migration tests on PostgreSQL backend."""
+    FIXTURE = test_fixtures.PostgresqlOpportunisticFixture