part-handler: add missing import
part-handler: add missing import

errno is used in the excption but not imported.

bug 1154887
Change-Id: I1c2961f08824d919ed2483a0a9cf54c50862f354

cryptickp/heat,openstack/heat,gonzolino/heat,jasondunsmore/heat,NeCTAR-RC/heat,takeshineshiro/heat,srznew/heat,rh-s/heat,cwolferh/heat-scratch,citrix-openstack-build/heat,dragorosson/heat,openstack/heat,miguelgrinberg/heat,takeshineshiro/heat,pratikmallya/heat,JioCloud/heat,noironetworks/heat,pratikmallya/heat,varunarya10/heat,redhat-openstack/heat,pshchelo/heat,NeCTAR-RC/heat,cwolferh/heat-scratch,gonzolino/heat,JioCloud/heat,maestro-hybrid-cloud/heat,maestro-hybrid-cloud/heat,steveb/heat,citrix-openstack-build/heat,rickerc/heat_audit,noironetworks/heat,rdo-management/heat,rh-s/heat,dims/heat,steveb/heat,dragorosson/heat,jasondunsmore/heat,rdo-management/heat,Triv90/Heat,varunarya10/heat,ntt-sic/heat,srznew/heat,Triv90/Heat,redhat-openstack/heat,dims/heat,Triv90/Heat,rickerc/heat_audit,pshchelo/heat,miguelgrinberg/heat,ntt-sic/heat,cryptickp/heat