Agreed that section of the docs should be more explicit in pointing out
that __getattr__ and __getattribute__ won't work for proxying special
methods for new-style classes.

It's also true that there are quite a few special methods where nothing
special is needed to correctly proxy the methods. That said, defining
all of the methods blindly is also bad (as a lot of informal type
testing is done by checking for certain special methods as attributes).

Perhaps it would be useful to have a method on type instances that could
be explicitly invoked to tell the type to run through all the tp_* slots
and populate them based on doing getattr(self, "__slotname__").

(Note that it's only those methods with dedicated slots in the C type
structure that are a problem here - those which are implemented solely
as normal Python methods like __enter__, __exit__ or the pickle module's
special methods can typically be overridden as expected through the use
of __getattr__ and __getattribute__)