Comment 20 for bug 1499647

what about the exception:
"DBReferenceError: (IntegrityError) (1452, 'Cannot add or update a child row: a foreign key constraint fails (`neutron`.`ha_router_agent_port_bindings`, CONSTRAINT `ha_router_agent_port_bindings_ibfk_2` FOREIGN KEY (`router_id`) REFERENCES `routers` (`id`) ON DELETE CASCADE)') 'INSERT INTO ha_router_agent_port_bindings (port_id, router_id, l3_agent_id, state) VALUES (%s, %s, %s, %s)' ('f368c83f-40aa-45b4-89b5-d0ae6424ebb1', 'a1e4b69c-21a5-4bd4-b5e8-7e7346b29d85', None, 'standby')\n"],

seems that the merged patch did not solve this.
There has race between ha router delete and router update.
I report a separated https://bugs.launchpad.net/neutron/+bug/1522268.
And the race will also cause the bug https://bugs.launchpad.net/neutron/+bug/1510757