Updated openstack/openstack
Project: openstack/keystone  0f6ad57ccd77e7931d681cb02a6c2aaa72046c33
null
Use abstract base class for policy driver

Use the abc module for managing abstract base classes in the driver
layer.

bp abstract-base-class-drivers

Change-Id: I33da50d35c932399aaec8e005215a0f8e7e2acdc