title: How to receive events about change of state of another supervisor service?
body: <p>I have a supervisord service 'launch' and I want to receive an event at every change of state of this service. (From STOPPED to STARTING for ex).</p>
  <p>One way of doing it would be to run <code>sudo supervisor status launch</code> every second, but I don't think that's the best way of doing it.</p>