Merge "Do not access DB when it is in maintenance mode."

hooks/horizon_hooks.py

@@ -75,6 +75,7 @@ from charmhelpers.contrib.openstack.utils import (
     CompareOpenStackReleases,
     series_upgrade_prepare,
     series_upgrade_complete,
+    is_db_maintenance_mode,
 )
 from charmhelpers.contrib.openstack.ha.utils import (
     generate_ha_relation_data,
@@ -394,6 +395,9 @@ def db_joined():
 @hooks.hook('shared-db-relation-changed')
 @restart_on_change(restart_map(), stopstart=True, sleep=3)
 def db_changed():
+    if is_db_maintenance_mode():
+        log('Database maintenance mode, aborting hook.')
+        return
     resolve_CONFIGS()
     if 'shared-db' not in CONFIGS.complete_contexts():
         log('shared-db relation incomplete. Peer not ready?')