Add Python3 xena unit tests

This is an automatically generated patch to ensure unit testing
is in place for all the of the tested runtimes for xena.

See also the PTI in governance [1].

[1]: https://governance.openstack.org/tc/reference/project-testing-interface.html

Change-Id: Ibc85c205093665b16c05092b6841c27e73aed7c1

Author: openstackadmin

.zuul.yaml

@@ -2,6 +2,6 @@
     templates:
       - check-requirements
       - horizon-non-primary-django-jobs
-      - openstack-python3-wallaby-jobs
+      - openstack-python3-xena-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3