Option "os_region_name" from group "placement" is deprecated

This deprecation warning was found in nova-compute.log:

2019-07-17 22:31:33.491 44637 WARNING oslo_config.cfg [req-36da0399-910d-4078-a2af-36132db31f54 - - - - -] Option "os_region_name" from group "placement" is deprecated for removal (Endpoint lookup uses the service catalog via common keystoneauth1 Adapter configuration options. Use the region_name option instead.). Its value may be silently ignored in the future.
2019-07-17 22:31:33.492 44637 WARNING oslo_config.cfg [req-36da0399-910d-4078-a2af-36132db31f54 - - - - -] Option "os_region_name" from group "placement" is deprecated. Use option "region-name" from group "placement".

Setup:

Bionic
OpenStack Queens
Juju 2.6.5
LXD containers [1]

LXD host:
Linux node-pytheas 4.15.0-54-generic #58-Ubuntu SMP Mon Jun 24 10:55:24 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

[1]: https://github.com/openstack-charmers/openstack-on-lxd