New submission from dubiousjim :
`Lib/os.py` has at line 464, in definition of `fwalk`:
```
if not isinstance(top, int) or not hasattr(top, '__index__'):
```
If I understand this test correctly, it should be requiring that the name/fd is
NEITHER an int NOR has an __index__ method.
dubiousjim added the comment:
In response to Issue #7105, self._pending_removals was added to
WeakValueDictionaries (and also WeakKeyDictionaries, but they're not relevant
to what I'm about to discuss). This was in changesets 58194 to tip and 58195 to
3.1, back in Jan 2010
