Fix tox<4 issue for zed job

Added task to install proper version
of tox(<4) so the job won't fail and
set the job as voting again

Story: 2010573
Change-Id: I0e9ad3632d16a5aa8c0e98d3e0d10bee79cead99

.zuul.yaml

@@ -10,8 +10,7 @@
         - python-tempestconf-tempest-devstack-admin-yoga
         # temporarily marked to n-v, there is a bug
         # https://storyboard.openstack.org/#!/story/2010573
-        - python-tempestconf-tempest-devstack-admin-zed:
-            voting: false
+        - python-tempestconf-tempest-devstack-admin-zed
         - python-tempestconf-tempest-devstack-demo
         - python-tempestconf-tempest-devstack-admin-plugins
         - python-tempestconf-tempest-devstack-enforce-scope-new-defaults-admin

playbooks/python-tempestconf-tempest-devstack.yaml

@@ -2,6 +2,16 @@
   roles:
     # the role is inherited from openstack/devstack project
     - run-devstack
+  tasks:
+    - name: Python-tempestconf tox<4 workaround
+      shell: |
+        python3 -m pip install "tox{{ ensure_tox_version }}"
+      args:
+        executable: /bin/bash
+      become: true
+      when:
+        - branch is defined
+        - branch in ["stable/zed"]
 
 - hosts: tempest
   vars: