Add link to issue 17911
Add link to issue 17911

The ongoing development in upstream python may
produce a useful class that we can use in the future
to reduce this objects code; so this adds a link to
that for future reference.

Change-Id: I86baa096e113cccbb4915ad4fd6fb8cc0313e0a0

pombredanne/taskflow-1,jimbobhickville/taskflow,junneyang/taskflow,openstack/taskflow,junneyang/taskflow,pombredanne/taskflow-1,jimbobhickville/taskflow,openstack/taskflow