def stop(self, signal=None):
        """Stop the heroku local subprocess and all of its children.
        """
        signal = signal or self.int_signal
        self.out.log("Cleaning up local Heroku process...")
        if self._process is None:
            self.out.log("No local Heroku process was running.")
            return

        try:
            os.killpg(os.getpgid(self._process.pid), signal)
            self.out.log("Local Heroku process terminated.")
        except OSError:
            self.out.log("Local Heroku was already terminated.")
            self.out.log(traceback.format_exc())
        finally:
            self._process = None
Stop the heroku local subprocess and all of its children.