I've seen this crash about 50 times in the UCSF Chimera molecular visualization package, same traceback, and it is caused when a tooltip is raised, but not from IDLE.  The key observation is that it only happens on dual display systems where the second display is positioned partly or entirely above or to the left of the primary display.  An attempt to raise a tooltip on that second display causes a crash.  This seems almost certain to be a Mac Tk bug.  At first I thought it was caused by the x,y screen position of the tool tip being negative.  But when the second screen is arranged above the primary screen (in Mac display system preferences) the y position is which increases from bottom to top is something like 2000, not negative.  Currently my hunch is that the tooltip popup window was created for the primary display, and trying to position it on the secondary display is for some reason an error.  I don't know enough about the native Mac NSWindow to say anything definitive.

Hope this helps you to at least consistently reproduce the crash.