> Haypo describes his complicated patch as "useful on Windows", 
> but not critical

Usecase on Windows: your japanese friend gives you an USB key (eg. created on Windows with code page 932) with his Python project, you cannot run it on your english speaking Windows (eg. code page 1252), because it loads Python modules with japanese characters in their paths.

It works if all paths are encodable to your ANSI code page. It doesn't work if a least one character of one path is not encodable to your ANSI code page.

I don't know if this usecase is common or not.

Note: the FAT file system of the USB key stores filenames as UTF-16 (and not in the user code page).