title: Sleep in async application, without blocking event loop
body: <p>I have a problem with one my async tests: tornado seems not to be up and running (I get 599s), even though it is started as a fixture. I would like to verify that it is indeed running, by doing the following:</p>
  
  <ol>
  <li>Start the test</li>
  <li>Before the requests are actually sent to tornado, I would like my code to "sleep" for a long time so that I can manually check with the browser that tornado is indeed running.</li>
  </ol>
  
  <p>How can I tell python to sleep without blocking the async loop? If I do <code>time.sleep</code>, the whole process (and thus the loop) is not responsive for the duration of the sleep.</p>