Ensure sphinx and sphinxcontrib-httpdomain are installed for doc builds
Ensure sphinx and sphinxcontrib-httpdomain are installed for doc builds

Change-Id: I1be2865a5d9809c030decaa71c415ca14228116b

cneill/designate-testing,cneill/designate-testing,richm/designate,ramsateesh/designate,cneill/designate-testing,kiall/designate-py3,tonyli71/designate,grahamhayes/designate,grahamhayes/designate,ionrock/designate,ramsateesh/designate,NeCTAR-RC/designate,cneill/designate,kiall/designate-py3,openstack/designate,melodous/designate,melodous/designate,richm/designate,melodous/designate,kiall/designate-py3,ionrock/designate,tonyli71/designate,openstack/designate,ionrock/designate,kiall/designate-py3,NeCTAR-RC/designate,grahamhayes/designate,muraliselva10/designate,cneill/designate,tonyli71/designate,melodous/designate,cneill/designate,muraliselva10/designate,kiall/designate-py3,cneill/designate,ramsateesh/designate,muraliselva10/designate,cneill/designate,openstack/designate