Comment by Macha

So it actually doesn't, it's basically just a hack around the fact that the repl is basically:

    while True:
        print(str(eval(input())))

Case in point:

    >>> x = str(quit)
    >>> x
    'Use quit() or Ctrl-Z plus Return to exit'

I suppose you could implement quit.__str__ as sys.exit(0), if you really wanted to avoid this problem.