[Python-porting] Pickling unbound methods on Python 3

["Martin v. Löwis"]

> What if we'll try the expensive stuff after the old way (shallow module
> search) fails and is about to raise an exception?

Feel free to submit a patch. However, if this needs to be fixed at all 
(and I'm not convinced it does), then I'd rather see a proper fix, i.e. 
one where you find the class from the function object directly, or which
has an even more general way of identifying global objects.

Regards,
Martin