Hi Virgil; thanks for stepping up to this.  Backward compatibility was 
largely for the sake of compatibility with Jython, which was always 
lagging far behind CPython.  I doubt it's a concern these days, and the 
unittest.py in the Python source repository should probably always be 
implemented in the nicest, cleanest way possible with the latest 
CPython.

Your changes look good to me, except for the KeyboardInterrupt one -- 
unless the way Ctrl-C is handled by Python has changed in the last 
couple of years, changing this "except:" clause will stop the text-mode 
test runner from being interruptible.  Admittedly the TextTestRunner 
should somehow be given an opportunity to detect Ctrl-C in order to stop 
when asked, but this diff does not allow for that.