migration: don't assume the mixin use provision4.16.0

In 2ad571c8d7a7e1d8d18f7c5e97c564509fd34816 we have changed the backend
used to cleanup the ModelsMigrationsSync by the one from
oslo_db.sqlalchemy.provision.

But in ModelsMigrationsSync, nothing uses the provisioning system. The
engine can be created outside oslo.db. And oslo.db must must not assume
it have been created by the oslo_db.sqlalchemy.provision module.

For example, 2ad571c8d7a7e1d8d18f7c5e97c564509fd34816 have broken the
Gnocchi models migration test that creates the engine itself.

This change builds a new backend to cleanup all database objects.

Change-Id: Ie8c454528ce3aa816c04fbb4beb69f4b5ec57e9c
Closes-bug: #1647280

1 files changed, 4 insertions, 5 deletions

diff --git a/oslo_db/sqlalchemy/test_migrations.py b/oslo_db/sqlalchemy/test_migrations.py
index 549654c..56beddb 100644
--- a/oslo_db/sqlalchemy/test_migrations.py
+++ b/oslo_db/sqlalchemy/test_migrations.py
@@ -595,11 +595,10 @@ class ModelsMigrationsSync(object):
             self.skipTest('sqlalchemy>=0.8.4 and alembic>=0.6.3 are required'
                           ' for running of this test: %s' % e)
 
-        # drop all tables after a test run
-        backend = provision.Backend.backend_for_database_type(
-            self.get_engine().name)
-        self.addCleanup(functools.partial(backend.drop_all_objects,
-                                          self.get_engine()))
+        # drop all objects after a test run
+        engine = self.get_engine()
+        backend = provision.Backend(engine.name, engine.url)
+        self.addCleanup(functools.partial(backend.drop_all_objects, engine))
 
         # run migration scripts
         self.db_sync(self.get_engine())