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: I6b35118b83af7c18baaefaddfdd6cd51912ee0c7

Author: openstackadmin

.zuul.yaml

@@ -2,7 +2,7 @@
     templates:
       - check-requirements
 #     - openstack-lower-constraints-jobs
-      - openstack-python3-wallaby-jobs
+      - openstack-python3-xena-jobs
       - openstackclient-plugin-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3