Fixup incorrect exception handler
Fixup incorrect exception handler

Change-Id: I85fec791f1c6aaee1fccc9508556ec2f828f2456

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