Updated openstack/openstack
Project: openstack/keystone  6751c7dc3b1b364e8f59d452f5702e89d4d56bcb
null
Clean up duplicate exceptions in docs for assignment.Driver

keystone.exception.ProjectNotFound was duplicated in the
docstrings for some of the methods in assignment.Driver.

Related-Bug: #1239476
Change-Id: I2e20eff1f307fdba2dd75097302b11c1e98949e3