title: is there a mongoose connect error callback
body: <p>how can i set a callback for the error handling if mongoose isn't able to connect to my DB?</p>
  
  <p>i know of</p>
  
  <pre><code>connection.on('open', function () { ... });
  </code></pre>
  
  <p>but is there something like</p>
  
  <pre><code>connection.on('error', function (err) { ... });
  </code></pre>
  
  <p>?</p>