The patch deprecates bytes filenames for the following functions:

nt._getfullpathname
nt._isdir
os.access
os.chdir
os.chmod
os.link
os.listdir
os.lstat
os.mkdir
os.open
os.rename
os.rmdir
os.stat
os.symlink
os.unlink
os.utime

Oh, I forgot a test for os.open(bytes).