Test a non-BMP Unicode character (a.k.a. emoji) in both 
file text only (not file name):

	A non-BMP emoji => 😊

This file can be opened in PyEdit with a File->Open (and, on
Mac, with Finder's drag-and-drops, Open Withs, and clicks).

It doesn't break the GUI or later open dialogs (thanks to both
Tk and tkinter-bug workarounds), but the emoji is replaced 
with the Unicode replacement character (the diamond question
mark) for display, and is replaced permanently if saved to files
(alas, full-scale emoji silliness must await a future Tk...).

The upside is that Unicode symbols in the U+0000..U+FFFF 
BMP (UCS-2) code-point range work fine in Tk and PyEdit:

	BMP Unicode symbols => ✓ ☓ ☑ ☒ ☀ ☼ ☉ ★ ☆ ☞ ☜