Make tools/pretty_tox.sh more informative and reliable
Make tools/pretty_tox.sh more informative and reliable

Change-Id: If541d88fedfad344bdfd87188007d7d293fd791a

openstack/sahara,tellesnobrega/sahara,egafford/sahara,tellesnobrega/sahara,zhangjunli177/sahara,egafford/sahara,zhangjunli177/sahara,crobby/sahara,crobby/sahara,crobby/sahara,zhangjunli177/sahara,openstack/sahara