When the :data:`tempfile.tempdir` global variable is set to a value of
type bytes, it is now handled consistently.  Previously exceptions
could be raised from some tempfile APIs when the directory did not
already exist in this situation.  Also ensures that the
:func:`tempfile.gettempdir()` and :func:`tempfile.gettempdirb()`
functions *always* return ``str`` and ``bytes`` respectively.
