__ipow__ method must ignore its third argument
|Reported by:||cwitty||Owned by:||somebody|
Evidently the Python position is that it's OK to pass garbage as the third argument of a .nb_inplace_pow() method; see http://bugs.python.org/issue1653736 and http://svn.python.org/view/python/branches/release25-maint/Objects/typeobject.c?r1=53690&r2=53689&pathrev=53690 . In this case, it might be a good idea to forbid the user from writing crashy code.
(I don't know how to trigger the particular call referenced above without the patch on #561, and the next version of that patch will be changed to avoid the problem. So I don't know of an actual test case for this problem.)