I think the main problem here is an impedance mismatch caused by forcing things to be Unicode. While the Python developers are technically correct (the best kind they say..) in claiming that LANG=C means ASCII, that's not how everything else in UNIX works until now, most applications don't crash because of encoding errors. And filenames are byte strings, so forcing Unicode on them is a bad idea.

It would be great if everyone fixed their locale settings and all their filename encodings but in the meantime this will cause even more friction for Python 3 adoption.