> This is not really my area of expertise, but I would have thought if you defined a __special__ method to something illegal (non-callable, or wrong signature) it would be reasonable for Python to raise an error at class definition (or assignment) time, not just later when you try to use it.

As Guido pointed out on the -ideas thread, defining __spam__ = None to block inheritance of a superclass implementation has long been the standard way to mark a class unhashable. So, any Python that raised such an error would break a lot of code. 

> Somewhere I think the documentation says you are only allowed to use these names as documented.

I can't find anything that says that. Any idea where to look? That might be worth adding, but if we add it at the same time as (or after) we explicitly document the None behavior, that's not a problem. :)

By the way, did you not review my last patch because you didn't get an email for it? I think Rietveld #439 (http://psf.upfronthosting.co.za/roundup/meta/issue439) may be causing issues to get stalled in the patch stage because people are expecting to get flagged when a new patch goes up but never see it (unless they're on the same mail domain as the patcher).