> IIUC, that usage is an equivalent transformation, i.e. the code doesn't
> change its behavior. It is mere refactorization.

I changed os.getenv() to accept byte string key (in a previous commit), but I don't like this hack. If we have os.environb, os.getenv() shouldn't support bytes anymore (but use str only, as before).

--

I worked a little more on fsencode()/os.environb, trying to fix all issues. fsdecode() is no more needed if we have os.environb, and fsencode() can be simplified to:

  def fsencode(value):
     return value.encode(sys.getfilesystemencoding(), 'surrogateescape')

fsdecode() leads to mojibake.