Fix installation on python3-only systems
Fix installation on python3-only systems

Change-Id: I8dd10ce459d9d3261317e098454f3e1adee666cd
Closes-Bug: 1455466

shdowofdeath/rally,amit0701/rally,vganapath/rally,vganapath/rally,cernops/rally,amit0701/rally,go-bears/rally,paboldin/rally,eonpatapon/rally,shdowofdeath/rally,aplanas/rally,aforalee/RRally,pyKun/rally,yeming233/rally,eayunstack/rally,openstack/rally,group-policy/rally,aforalee/RRally,redhat-openstack/rally,group-policy/rally,yeming233/rally,openstack/rally,amit0701/rally,paboldin/rally,vganapath/rally,afaheem88/rally,paboldin/rally,group-policy/rally,cernops/rally,openstack/rally,pyKun/rally,afaheem88/rally,vefimova/rally,vganapath/rally,aplanas/rally,gluke77/rally,gluke77/rally,gluke77/rally,vponomaryov/rally,vponomaryov/rally,eayunstack/rally,openstack/rally,eayunstack/rally,go-bears/rally,gluke77/rally,eonpatapon/rally,vefimova/rally,redhat-openstack/rally