Here's an updated patch, plus support for a second attribute that I need for #10854. I previously wrote a patch that does this same thing for that issue, but this one handles things a lot more nicely :)

I renamed "module_name" to just be "name" since I was adding "path" and didn't want to have to name it "module_path" and have two "module_" attributes since I think it's clear what they are for. We can go back to "module_" names if you want - no big deal.

It's really just the same patch as before but updated for a few minor changes (the ComplexExtendsException sig changed), and the moving of keyword handling in ImportError_init into a macro since we have to do the same initialization twice now. I'm not married to that implementation, it just minimized duplication and seems to work alright.

Also, this removes the import.c change (see Brett's last message).