> You should also support bytearray() in ntpath:
>    isinstance(path, (bytes, bytearray))

The most generic way of allowing all bytes-alike objects is to write:
    path = bytes(path)

It raises a TypeError if `path` can't export a read-only buffer of
contiguous bytes; also, it is a no-op if `path` is already a bytes
object, so very cheap in the common case.