Comment 13 for bug 1614576

I followed the test case and upgraded from Trusty to Xenial without an issue.

2016-11-14 11:16:21,125 INFO release-upgrader version '16.04.18' started
2016-11-14 11:16:21,141 INFO locale: 'en_US' 'UTF-8'
2016-11-14 11:16:21,188 DEBUG setting up environ for non-interactive use
...
2016-11-14 11:39:55,996 DEBUG quirks: running PostCleanup
2016-11-14 11:39:55,996 DEBUG running Quirks.PostCleanup
2016-11-14 11:39:55,996 DEBUG Running PostInstallScript: './xorg_fix_proprietary.py'
2016-11-14 11:39:56,011 DEBUG confirmRestart() called