Message 218983 - Python tracker

I tested the patch and it looks correct upon inspection. It looks like it applies cleanly and a straight forward solution. 

I made a slight change so that when the Demo exits, it has a better message. I also added the change to the NEWS.txt file. 

I also ran the IDLE tests, and everything passed. I didn't see new tests added, but I am not sure if that is needed, since we are just adding a menu binding.

I've attached my patch with the changes listed above. It should be ready for review.