Updated openstack/openstack
Project: openstack/keystone  b6843ded671ffe859d8cb254acc696a475af73cf

install gettext on OS X for msgfmt

as already mentioned by this doc, gettext provides msgfmt, which is
required for i18n validation via tox.

Change-Id: I4cae5fddc42897615554746f946ed4f490dc1ca5