Comment 3 for bug 1563101

Reviewed: https://review.openstack.org/296140
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=5107da7610ef8afbc5802f79e8d1a48c8c6deb77
Submitter: Jenkins
Branch: master

commit 5107da7610ef8afbc5802f79e8d1a48c8c6deb77
Author: Ronald De Rose <email address hidden>
Date: Wed Mar 23 01:32:20 2016 +0000

    Remove backend interface and common code out of identity.core

    This removes dependencies where backend code references code in the
    core. The reasoning being that the core should know about the backend
    interface, but the backends should not know anything about the core
    (separation of concerns). And part of the risk here is a potential for
    circular dependencies.

    - Moved the filter_user method to backends/base.py. This method is
    only used by the backends.

    - Moved the interfaces (base) to modules inside the backends. Interfaces
    should be closer to the code that implements them and again, wanted to
    remove the dependency where the backends were referencing code in the
    core.

    Partial-Bug: #1563101

    Change-Id: I5ff9c4e4b6d64750f5db2a73cc4317358aea0649