title: What is the chalice @app.schedule syntax for cron events?
body: <p>I am trying to follow the documentation from <a href="https://chalice.readthedocs.io/en/latest/topics/events.html" rel="nofollow noreferrer">https://chalice.readthedocs.io/en/latest/topics/events.html</a></p>
  
  <p>I tried this</p>
  
  <pre><code>@app.schedule('0 0 * * ? *')
  def dataRefresh(event):
      print(event.to_dict())
  </code></pre>
  
  <p>and got this error:</p>
  
  <blockquote>
    <p>botocore.exceptions.ClientError: An error occurred
    (ValidationException) when calling the PutRule operation: Parameter
    ScheduleExpression is not valid.</p>
  </blockquote>
  
  <p>and so tried this:</p>
  
  <pre><code>@app.schedule(Cron('0 0 * * ? *'))
  def dataRefresh(event):
      print(event.to_dict())
  </code></pre>
  
  <p>and got this other error:</p>
  
  <blockquote>
    <p>NameError: name 'Cron' is not defined</p>
  </blockquote>
  
  <p>Nothing works... what's the correct syntax?</p>