six is also a required dependency
six is also a required dependency

Found this because monasca-notification aborted before
monasca-agent was installed in the virtual environment

Change-Id: Ib1eea8afde785ecadeac69d21ea6dd831f55b0ed

stackforge/monasca-notification,openstack/monasca-notification,sapcc/monasca-notification,openstack/monasca-notification