Sync with Oslo

This fixes a bunch os Python3-related issues, linked to iteritems(), urllib,
encoding, etc.

This is now up-to-date with 6827012438c7c88e0f54803f33c612684cf34e86 in Oslo.

Change-Id: Id8c265d76abfd8ede5575d3903f612ad1ea46643
Merge "Sync with Oslo"