[Openstack-stable-maint] Stable check of openstack/oslo.serialization for ref refs/heads/stable/train failed

Build failed. https://zuul.opendev.org/t/openstack/buildset/3e63ddb3328248ff87a1bcbcb73367... - openstack-tox-docs https://zuul.opendev.org/t/openstack/build/0579c4e2768948d2a168211fd2e1f838 : SUCCESS in 3m 03s - openstack-tox-py27 https://zuul.opendev.org/t/openstack/build/3294eacdd4d14003bbed565d94b78209 : SUCCESS in 3m 33s - openstack-tox-py36 https://zuul.opendev.org/t/openstack/build/21b064a38d0b434a8ce1f1d27a5f835a : SUCCESS in 3m 55s - openstack-tox-py37 https://zuul.opendev.org/t/openstack/build/a553017e2f654235805f61826fe96b5a : FAILURE in 4m 13s