[docs] [issue13402] Document absoluteness of sys.executable

Philip Jenvey <pjenvey@underboss.org> added the comment: sys.executable can be None on Jython (and I believe IronPython) when ran in an 'embedded' mode ---------- nosy: +dino.viehland, pjenvey _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue13402> _______________________________________