title: Use of unresolved identifier 'PHPhotoLibrary'
body: <p>I am working on a Photos extension for Mac OS X (10.11).</p>
  
  <p>I have the Photos and PhotosUI frameworks imported. </p>
  
  <p>Everything is ok apart from when I try to make a call to PHPhotoLibrary.sharedPhotoLibrary().</p>
  
  <p>This results in an error in Xcode 7.3.1 (7D1014):</p>
  
  <pre><code>Use of unresolved identifier 'PHPhotoLibrary'
  </code></pre>
  
  <p>Has anyone else experienced this or know what could be causing the issue?</p>