Pbr requirement went missing
Pbr requirement went missing

Not really sure where the pbr requirement
went but making sure its defined in the
requirements file so that it gets included
when building.

Change-Id: Ie332fc0c9ad39e303b18812500bb07086d78f4ab

jimbobhickville/taskflow,openstack/taskflow,varunarya10/taskflow,jimbobhickville/taskflow,varunarya10/taskflow,pombredanne/taskflow-1,junneyang/taskflow,citrix-openstack-build/taskflow,openstack/taskflow,pombredanne/taskflow-1,junneyang/taskflow,citrix-openstack-build/taskflow