Dražen: didn't do a deep review, but a cursory look suggests the patch is fine.

As for having to change a ton of files to start using the attribute, that's part of the effect of changing something as basic as an exception. If you would rather break it up into separate patches that's fine. But I would caution you from doing more than this patch as I have gotten some push back from other core devs on my proposed new attributes on exceptions so I don't want you spending your time on something that might get sunk (although if you are enjoying it then go for it since if it gets accepted this work will be needed).

Also please sign the contributor agreement form (http://python.org/psf/contrib/contrib-form/) so that we can actually use your code.

Andrea: While the attribute might coincidentally name an attribute that is the same as some other attribute which is not the actual trigger, the traceback on the exception provides the proper context to know what attribute in what code did the actual triggering. The point is that the exception can be considered better than nothing and is still an improvement over not having the information at all.