I applied the changes from https://review.openstack.org/#/c/559932/2/neutron/db/l3_agentschedulers_db.py and https://review.openstack.org/#/c/559932/2/neutron/tests/unit/db/test_agentschedulers_db.py, error messages are now gone after rebooting instance.
I applied the changes from https:/ /review. openstack. org/#/c/ 559932/ 2/neutron/ db/l3_agentsche dulers_ db.py and https:/ /review. openstack. org/#/c/ 559932/ 2/neutron/ tests/unit/ db/test_ agentschedulers _db.py, error messages are now gone after rebooting instance.