Switch to using enginefacade

Closes-Bug: #2067345
Change-Id: If9a2c96628cfcb819fee5e19f872ea015979b30f

Author: mnaser

magnum/common/context.py

@@ -12,6 +12,7 @@
 
 from eventlet.green import threading
 from oslo_context import context
+from oslo_db.sqlalchemy import enginefacade
 
 from magnum.common import policy
 
@@ -20,6 +21,7 @@
 CONF = magnum.conf.CONF
 
 
+@enginefacade.transaction_context_provider
 class RequestContext(context.RequestContext):
     """Extends security contexts from the OpenStack common library."""
 

magnum/db/sqlalchemy/alembic/env.py

@@ -13,8 +13,8 @@
 from logging import config as log_config
 
 from alembic import context
+from oslo_db.sqlalchemy import enginefacade
 
-from magnum.db.sqlalchemy import api as sqla_api
 from magnum.db.sqlalchemy import models
 
 # this is the Alembic Config object, which provides
@@ -43,7 +43,7 @@ def run_migrations_online():
     and associate a connection with the context.
 
     """
-    engine = sqla_api.get_engine()
+    engine = enginefacade.writer.get_engine()
     with engine.connect() as connection:
         context.configure(connection=connection,
                           target_metadata=target_metadata)