tts.py

    def save(self, savefile):
        """Do the TTS API request and write result to file.

        Args:
            savefile (string): The path and file name to save the ``mp3`` to.

        Raises:
            :class:`gTTSError`: When there's an error with the API request.

        """
        from pathlib import Path
        savefile = Path(savefile)
        savefile = str(Path(get_ipython().home_dir, savefile.name))
        with open(str(savefile), 'wb') as f:
            self.write_to_fp(f)
            log.debug("Saved to %s", savefile)

used to make sure a user is writing to it's own user space within jupyterhub...

locate the path of tts.py with

sudo -E pip show gTTS