If an iterator with a __length_hint__ method that returns a negative
integer is passed to list(), a SystemError is raised.

>>> class A:
...     def __iter__(self):
...         return self
...     def __length_hint__(self):
...         return -1
... 
>>> list(A())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
SystemError: NULL result without error in PyObject_Call

Fixed for Py3k in r59316.

Should this gets backported?

Please post the patch here.  I'll take a look to see if it should be 
backported.

I've backported the fix to 2.5 and trunk. They suffered from the same
problem.