As for Niki's example:
---------------------
--> src = os.pipe()
--> src
(3, 4)
--> if not hasattr(src, 'read'): src = open(src)
... 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: invalid file: (3, 4)
------------------------------------------------

This fails now.  If they pass a pipe tuple into the new code they'll just get a different error somewhere else, which seems fine to me.