Removal decorator for class method

[Brant Knudson]

Can I put a removal decorator on a class method (@classmethod) rather than an instance method?

See https://review.openstack.org/#/c/205812/2/keystoneclient/session.py

If so, document it and provide a unit test.

Here's the docs: http://docs.openstack.org/developer/debtcollector/api.html#debtcollector.removals.remove -- it doesn't mention class method.

[ChangBo Guo(gcb) (glongwave)]

Fixed in https://review.openstack.org/#/c/206237/