> FindFirst/NextFileA will also do some other interesting conversions,
> such as the best-fit conversion (which the "mbcs" code doesn't do
> (anymore?)).

About mbcs, mbcs codec of Python 3.1 is like .encode('mbcs', 'replace') and 
.decode('mbcs', 'ignore') of Python 3.2 (see issue #850997). By default 
(strict error handler), it now raises errors on undecodable byte sequence and 
unencodable character, whereas Python 3.1 just ignores the error handler.

PyUnicode_EncodeFSDefault / PyUnicode_DecodeFSDefault uses the strict error 
handler.

I just added a note about mbcs in Doc/whatsnew/3.2.rst: r84750.