procutil: make _make_write_all() function private Because this function isn’t meant for general use (e.g., it’s Python 2-only), make in a module-private function by prefixing it with `_`.

dispatch: handle late KeyboardInterrupt occurred in run() User can press Ctrl+C while flushing streams in dispatch.run(). In such case, I think exiting with 255 is better than printing Python traceback and exiting with 1.