Unable to freeze job graph: Unable to modify final job <Job publish-openstack-releasenotes branches: None source: openstack-infra/project-config/zuul.d/jobs.yaml@master#26> attribute variables={'sphinx_python': 'python3'} with variant <Job publish-openstack-releasenotes branches: None source: openstack-infra/openstack-zuul-jobs/zuul.d/project-templates.yaml@master#298>