Use alembic upgrade function/command directly

Instead of implementing a similar version to what the
upgrade function does, just use it directly instead.

Change-Id: I61a3c9f09c6e0724f2b55951989171ef4aaafe0c

taskflow/persistence/backends/sqlalchemy/alembic/env.py

@@ -60,18 +60,16 @@ def run_migrations_online():
     and associate a connection with the context.
 
     """
-    engine = engine_from_config(config.get_section(config.config_ini_section),
-                                prefix='sqlalchemy.',
-                                poolclass=pool.NullPool)
-
-    connection = engine.connect()
-    context.configure(connection=connection, target_metadata=target_metadata)
-
-    try:
+    connectable = config.attributes.get('connection', None)
+    if connectable is None:
+        connectable = engine_from_config(
+            config.get_section(config.config_ini_section),
+            prefix='sqlalchemy.', poolclass=pool.NullPool)
+    with connectable.connect() as connection:
+        context.configure(connection=connection,
+                          target_metadata=target_metadata)
         with context.begin_transaction():
             context.run_migrations()
-    finally:
-        connection.close()
 
 
 if context.is_offline_mode():

taskflow/persistence/backends/sqlalchemy/migration.py

@@ -18,25 +18,16 @@
 
 import os
 
-from alembic import config as a_config
-from alembic import environment as a_env
-from alembic import script as a_script
+from alembic import command
+from alembic import config
 
 
-def _alembic_config():
+def _make_alembic_config():
     path = os.path.join(os.path.dirname(__file__), 'alembic', 'alembic.ini')
-    return a_config.Config(path)
+    return config.Config(path)
 
 
 def db_sync(connection, revision='head'):
-    script = a_script.ScriptDirectory.from_config(_alembic_config())
-
-    def upgrade(rev, context):
-        return script._upgrade_revs(revision, rev)
-
-    config = _alembic_config()
-    with a_env.EnvironmentContext(config, script, fn=upgrade, as_sql=False,
-                                  starting_rev=None, destination_rev=revision,
-                                  tag=None) as context:
-        context.configure(connection=connection)
-        context.run_migrations()
+    cfg = _make_alembic_config()
+    cfg.attributes['connection'] = connection
+    command.upgrade(cfg, revision)