Process all log messages, until `stop()` is called. Intended to run
        in its own thread.

def run(self):
        """
        Process all log messages, until `stop()` is called. Intended to run
        in its own thread.
        """
        while True:
            msg = self._queue.get()
            if msg is _SHUTDOWN:
                break
            if self._enabled:
                print msg