Some comments about the patch:

- It seems wasteful to allocate a new PyUnicode object for the "."; the 
posix implements does it right: a simple wcscopy should be enough (and 
reduces the chances of refcount mistakes)

- the last block is not correctly indented; this code uses tabs.

- no need to test for hasattr(posix, 'listdir'): all supported platforms 
have directories and the posix module always exposes this function.