Log Message:
py-pbr: updated to 6.1.0

6.1.0

* Add openstack-tox-py312 as non-voting job
* Add SetupTools to our functional testing venvs
* Use SetupTools' vendored distutils in tests
* Also run coverage tests serially
* zuul: Drop retired repos from required-projects
* Drop Focal integration testing
* Omnibus PBR CI fixups
* Serialize tests
* Fix tempest-full job
* Use summary for the package summary
* Test on py310 and py311