Merge "CI: Install tox" into stable/stein

Author: Zuul

tests/playbooks/pre.yml

@@ -15,3 +15,8 @@
       file:
         path: "{{ kolla_build_logs_dir }}"
         state: directory
+
+    - name: Ensure tox is installed
+      pip:
+        name: tox
+      become: true