Remove dependent module py3kcompat

Module py3kcompat was removed from oslo-incubator, we can use
six directly.

Change-Id: I6c4266b71312ae53ecaedbd2ce1a865e60eb8d50
Closes-Bug: #1280033
Cast the quota set values to integer before checking their validity

Change-Id: I56409607d435a5e2ff702ccb9f19c5d12b432570
Closes-Bug: #1280159
Merge "Remove dependent module py3kcompat"
Merge "Cast the quota set values to integer before checking their validity"