Updated openstack/openstack
Project: openstack/keystone  1f52b644140535a0079cd6ff2f5c4b736270f1bb

Cleanup superfluous string comprehension and coersion

Remove the superfluous string comprehension and coersion to string
type in a join within the keystone.notifications module. The elements
in the namedtuple are already string types.

Change-Id: I107102fabc2f6671e10bcf1b5db40529fdb19d69