python312Packages.pbr: fix python 3.12 compatibility; python312Packages.openstackdocstheme: allow for python 3.12; openstack for python 3.12

python312Packages.pbr: fix python 3.12 compatibility; python312Packages.openstackdocstheme: allow for python 3.12; openstack for python 3.12 #138541