Add role assignments list support to identity v3

The assignments manager and its test class were created.
Some fake stubs were also added on the fakes.py module.

The "openstack role assignment list" command was created.

Change-Id: Iae94f4fee608ea3e09ff38961ad22edc38efb89c
Implements: blueprint roles-assignment-list
Closes-Bug: 1246310
Merge "Add role assignments list support to identity v3"
Ignore most of the new hacking 0.9.2 rules

So we can update requriements.txt.  But fix a couple of easy ones:
* Fix E251 (1 occurrance)
* Fix E131 (1 occurrance)

Change-Id: I62aaa423aa6da9e9f0ca026ec586b51cc6a6df03
Merge branch 'review/qiu_yu/refactor-role-list-cmd' into dt-test
Merge branch 'hacking-hack' into dt-test
Merge branch 'timings' into dt-test