title: Promises and irregular callbacks
body: <p>I'm playing around with a promises control flow, using <a href="https://github.com/petkaantonov/bluebird">bluebird</a>.  Bluebird provides a .promisify() method for converting a regular callback function into a promise function, but I'm unclear what I should be doing when the function is irregular.  For example the method signature for a <a href="https://github.com/mikeal/request">requestjs</a> request is </p>
  
  <pre><code>request(url, callback)
  </code></pre>
  
  <p>where callback is</p>
  
  <pre><code>err, res, body
  </code></pre>
  
  <p>instead of the regular</p>
  
  <pre><code>err, res
  </code></pre>
  
  <p>How should I be converting this to a promise?</p>