I wrote this patch to make confstr() return bytes (with code
similar to 2.x), and document the change in "Porting to Python
3.2" and elsewhere, but it then occurred to me that you might
have been talking about making a separate bytes API like
os.environb.  Which did you have in mind?

There is another option for a str API, which is to decode the
value as ASCII with the surrogateescape error handler.  The
returned string will then round-trip correctly through
PyUnicode_FSConverter(), etc., as long as the file system
encoding is compatible with ASCII, which PEP 383 requires it to
be.  This is how undecodable command line arguments are currently
handled when mbrtowc() is unavailable.