Looks like the retype is hitting an in-use volume:
http://logs.openstack.org/91/593191/1/gate/openstack-tox-py27/c473645/job-output.txt.gz#_2018-09-20_19_04_05_904948
2018-09-20 19:04:05.904948 | ubuntu-xenial | call('volume:retype', target_obj=Volume(_name_id=None,admin_metadata={},attach_status='detached',availability_zone='nova',bootable=False,cluster=<?>,cluster_name=None,consistencygroup=<?>,consistencygroup_id=None,created_at=2018-09-20T19:03:12Z,deleted=False,deleted_at=None,display_description='',display_name='test-multiattachvol',ec2_id=None,encryption_key_id=None,glance_metadata=<?>,group=<?>,group_id=None,host=None,id=d6aa12e8-5526-4eac-abdf-00196959fbdd,launched_at=None,metadata={},migration_status=None,multiattach=False,previous_status='available',project_id='7f265bd4-3a85-465e-a899-5dc4854a86d3',provider_auth=None,provider_geometry=None,provider_id=None,provider_location=None,replication_driver_data=None,replication_extended_status=None,replication_status=None,scheduled_at=None,service_uuid=None,shared_targets=True,size=1,snapshot_id=None,snapshots=<?>,source_volid=None,status='in-use',terminated_at=None,updated_at=2018-09-20T19:03:12Z,user_id='c853ca26-e8ea-4797-8a52-ee124a013d0e',volume_attachment=<?>,volume_type=VolumeType(f2416a1f-c3e3-4c86-8086-a04dab97319f),volume_type_id=f2416a1f-c3e3-4c86-8086-a04dab97319f))]
2018-09-20 19:04:05.909068 | ubuntu-xenial | 2018-09-20 19:03:12,396 INFO [cinder.volume.api] Invalid volume_type passed, retypes affecting multiattach are only allowed on available volumes, the specified volume however currently has a status of: in-use.
http://logstash.openstack.org/#dashboard/file/logstash.json?query=message%3A%5C%22call('volume%3Aretype'%5C%22%20AND%20message%3A%5C%22status%3D'in-use'%5C%22%20AND%20tags%3A%5C%22console%5C%22&from=7d
34 hits in 7 days, check and gate, stable/queens - maybe this is fixed in stein but not backported?
