It seems to me that it isn't tab completion's place to out think the
__dir__ method. A) Because the documentation doesn't tell you that it
does (although you are warned that it may call some stuff) and B)
because if someone set up a __dir__ method, they probably are listing
the things that they want listed for a particular reason. I think that
it would be less confusing for rlcompleter to follow the __dir__ method
when it exists and only do its own poking and prodding when it does not.