> I would consider it preferable if it quit 

Note that if we catch the error there might be no reason for IDLE to quit (unless the error left IDLE in some invalid state).

> with an error traceback that gave as much info as available,

That might scare newbies away.

> or if there is none, just said "IDLE has met an unexpected problem.", 

So this might be better for all the cases.

> perhaps followed by something like "Pleaee note the circumstances and
> make a report of the tracker is there is none already."

The first message could offer a "Report the problem" option that links to the tracker.  In theory we could also have a way to auto-fill the tracker issue, but that might lead to duplicates.