[Merge] ubuntu-release-upgrader:python-is-python2 into ubuntu-release-upgrader:ubuntu/master

[Dimitri John Ledkov]

Tested in a chroot upgrades.
-- 
https://code.launchpad.net/~ubuntu-core-dev/ubuntu-release-upgrader/+git/ubuntu-release-upgrader/+merge/381203
Your team Ubuntu Core Development Team is requested to review the proposed merge of ubuntu-release-upgrader:python-is-python2 into ubuntu-release-upgrader:ubuntu/master.