[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/3c03c910f3304f8da3f044fe177a7a... - openstack-tox-docs https://zuul.opendev.org/t/openstack/build/295454c65676417ea0eb641a43b88916 : SUCCESS in 3m 00s - openstack-tox-py27 https://zuul.opendev.org/t/openstack/build/37de21e6b66640f6ab8ae992db79f78d : RETRY_LIMIT in 2m 15s - openstack-tox-py36 https://zuul.opendev.org/t/openstack/build/6348bd7b7bd74d3799a103c3b0024d10 : SUCCESS in 2m 35s - openstack-tox-py37 https://zuul.opendev.org/t/openstack/build/21d88d50b790481ba0a5c9d7d4938bba : SUCCESS in 3m 05s