Merge "add python 3.7 unit test job"

Author: Zuul

.zuul.yaml

@@ -194,6 +194,7 @@
       - openstack-python-jobs
       - openstack-python35-jobs
       - openstack-python36-jobs
+      - openstack-python37-jobs
       - publish-openstack-docs-pti
       - check-requirements
       - release-notes-jobs-python3