Merge "Switch py36 jobs to centos-8"

zuul.d/jobs.yaml

@@ -174,6 +174,24 @@
     name: openstack-tox-py36
     parent: openstack-tox
     nodeset: ubuntu-bionic
+    branches: ^(stable/(stein|train|ussuri)).*$
+    timeout: 2400
+    description: |
+
+      Run unit tests for an OpenStack Python project under cPython
+      version 3.6.
+
+      Uses tox with the ``py36`` environment.
+    irrelevant-files: *common-irrelevant-files
+    vars:
+      tox_envlist: py36
+      bindep_profile: test py36
+
+- job:
+    name: openstack-tox-py36
+    parent: openstack-tox
+    nodeset: centos-8
+    branches: ^(?!stable/(stein|train|ussuri)).*$
     timeout: 2400
     description: |