Metaclass Python 3.x Compatibility
Metaclass Python 3.x Compatibility

use "six.add_metaclass" instead of "__metaclass__"

Change-Id: I57390fec40afe3a965be3215db8f79b9cf862a70

psachin/swift,smerritt/swift,levythu/swift,tipabu/swift,thiagodasilva/swift,tipabu/swift,mjzmjz/swift,hurricanerix/swift,bradleypj823/swift,matthewoliver/swift,larsbutler/swift,notmyname/swift,hbhdytf/mac,revoer/keystone-8.0.0,takeshineshiro/swift,Em-Pan/swift,openstack/swift,bradleypj823/swift,clayg/swift,hbhdytf/mac,Akanoa/swift,openstack/swift,hbhdytf/mac2,tipabu/swift,redhat-openstack/swift,prashanthpai/swift,williamthegrey/swift,matthewoliver/swift,mjwtom/swift,aerwin3/swift,clayg/swift,swiftstack/swift,notmyname/swift,bkolli/swift,smerritt/swift,rackerlabs/swift,dencaval/swift,hurricanerix/swift,bkolli/swift,hurricanerix/swift,clayg/swift,hbhdytf/mac2,larsbutler/swift,shibaniahegde/OpenStak_swift,mjzmjz/swift,psachin/swift,Em-Pan/swift,openstack/swift,redhat-openstack/swift,takeshineshiro/swift,bouncestorage/swift,rackerlabs/swift,gold3bear/swift,tipabu/swift,notmyname/swift,revoer/keystone-8.0.0,redbo/swift,hurricanerix/swift,nadeemsyed/swift,smerritt/swift,nadeemsyed/swift,nadeemsyed/swift,redbo/swift,daasbank/swift,gold3bear/swift,swiftstack/swift,mjwtom/swift,psachin/swift,matthewoliver/swift,notmyname/swift,thiagodasilva/swift,nadeemsyed/swift,daasbank/swift,levythu/swift,hbhdytf/mac2,hbhdytf/mac2,bouncestorage/swift,williamthegrey/swift,aerwin3/swift,matthewoliver/swift,prashanthpai/swift,openstack/swift,clayg/swift,shibaniahegde/OpenStak_swift,smerritt/swift,swiftstack/swift,dencaval/swift,Akanoa/swift,psachin/swift