Manually add pk for alembic_version table

We hit a problem that Neutron migrations cannot be applied
on galera cluster with ENFORCING mode as alembic_version table
missing primary key on the table and it is expected that all tables
will have primary keys.

alembic_version is created and managed by Alembic and fixes for this
on Alembic side are on the review [1]. Anyway here migration is
proposed that will add pk on this table if it is missing, as in
other case we will have inconsistency between new deployments and
old ones.

[1] - https://gerrit.sqlalchemy.org/#/c/279/

Change-Id: I543a1ee286bdf11ae35adb87125d044a351a2648
Closes-bug: #1655610

neutron/db/migration/__init__.py

@@ -212,3 +212,11 @@ def remove_fks_from_table(table, remove_unique_constraints=False):
         yield
     finally:
         create_foreign_keys(table, foreign_keys)
+
+
+def pk_on_alembic_version_table():
+    inspector = reflection.Inspector.from_engine(op.get_bind())
+    pk = inspector.get_pk_constraint('alembic_version')
+    if not pk['constrained_columns']:
+        op.create_primary_key(op.f('pk_alembic_version'),
+                              'alembic_version', ['version_num'])

neutron/db/migration/alembic_migrations/versions/EXPAND_HEAD

@@ -1 +1 @@
-5cd92597d11d
+929c968efe70

neutron/db/migration/alembic_migrations/versions/kilo_initial.py

@@ -25,6 +25,7 @@ revision = 'kilo'
 down_revision = None
 
 
+from neutron.db import migration
 from neutron.db.migration.alembic_migrations import agent_init_ops
 from neutron.db.migration.alembic_migrations import brocade_init_ops
 from neutron.db.migration.alembic_migrations import cisco_init_ops
@@ -49,6 +50,7 @@ from neutron.db.migration.alembic_migrations import vpn_init_ops
 
 
 def upgrade():
+    migration.pk_on_alembic_version_table()
     agent_init_ops.upgrade()
     core_init_ops.upgrade()
     l3_init_ops.upgrade()

neutron/db/migration/alembic_migrations/versions/ocata/expand/929c968efe70_add_pk_version_table.py

@@ -0,0 +1,33 @@
+# Copyright 2017 OpenStack Foundation
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+#
+
+"""add_pk_version_table
+
+Revision ID: 929c968efe70
+Revises: 5cd92597d11d
+Create Date: 2017-01-12 07:17:33.677770
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '929c968efe70'
+down_revision = '5cd92597d11d'
+
+
+from neutron.db import migration
+
+
+def upgrade():
+    migration.pk_on_alembic_version_table()