Add Python3 yoga unit tests
Add Python3 yoga unit tests

This patch updates the project template to use the Yoga project template
to ensure unit testing is in place for all of the tested runtimes
for yoga. For more please refer to [1].

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

Change-Id: I47f85706b2b5ad8ac12ac67e97b5bb7179572615

openstack/oslo.concurrency