> Why is that? In msg104063, you claim that you want to create these
> functions to deal with file names (not environment variables)

Yes, but my os_path_fs_encode_decode-3.patch uses it in getenv() which is maybe a bad idea: os.environb may avoid this.

> in msg104064, you claim that #8513 (which is about the program name in
> subprocess) would benefit from these functions. Do these use cases
> become invalid if os.environb becomes available?

#8513 is also related to environment variables: subprocess._execute_child() calls os.get_exec_path() which search the PATH environment variable. It would be nice to support bytes environment variable in the env argument of Popen constructor (bytes key and/or value).