DCD-386: Use the six module to paper over Python changes.

bin/run-all-tests

@@ -5,7 +5,7 @@ set -e
 # Use Ansible from virtualenv if provided
 if [[ -f .venv/bin/ansible ]]; then
     source .venv/bin/activate
-    pip install molecule docker
+    pip install molecule docker six
 fi
 
 for role in `find roles/ -name molecule`; do