Martin, I got your message after I submitted the last one.

This issue does involve IDLE crashing, but it's not crashing due to non-BMP characters. That is a side-effect of a bigger issue with pythonw.exe. See Issue13582 for more information.

IDLE's shell output has a gross deficiency due to Tkinter's inability to handle Unicode properly. Why penalize a program for running in IDLE just because IDLE can't write something to the text widget? This is precisely what your approach is doing - making IDLE an even more restricted environment than it needs to be.