Upgrade six to 1.5.2

six 1.5.2 has supported more modules for python 2 and 3 compatibility.

Change-Id: Iae1f2d730890829a89393c23a599848dfe72f792
Allow projects to use oslo.vmware

Change-Id: I389ddf0b1765d53bf9d02a71827021505190e188
Merge "Allow projects to use oslo.vmware"
Merge "Upgrade six to 1.5.2"