testing: make Eq(nan,<meh>) return False, Ne(nan, <meh>) return True

Not necessarily intended for a merge...
How about picking one random thing in the list to test it because the code certainly doesn't support the need for all these tests. So if you are trying to safeguard against any special case then a random test will eventually show the error. I think `choose` or `choice` (something like that) could be used from the random module.