I checked that -m idlelib acts the same as -m idlelib.idle, and that there is still a problem after opening a second editor window after the original. So the messages seem tied to not opening a shell window. In testing the patch, I noticed that exceptions are now occurring in all three .__del__ methods. With the candidate release imminent, I decided to only fix what is broken and only apply to 3.4 and not worry now about possible merge problems in the future.