Many scripts, such as tl-umount-localdrives, has code which looks like this: username = os.getenv("USER", "").lower() This does not work correctly with non-ASCII characters. We need to determine the locale and decode accordingly. I'm not sure how big this problem is, it should only affect you if you are using UPPERCASE non-ASCII characters.
This should all have been handled when we moved to Python 3 in bug 4586.