title: Unable to update to Xcode 8
body: <p>I would like to update to Xcode 8, but when I start the App Store it just shows me an <code>Open</code> button, but my existing Version is 7.3.1</p>
  
  <p>The requirements should be El Capitan 10.11.5 - I have 10.11.6 installed. </p>
  
  <p>Why is there no <code>Update</code> button?</p>
  
  <p><a href="https://i.stack.imgur.com/YGJnT.png"><img src="https://i.stack.imgur.com/YGJnT.png" alt="enter image description here"></a></p>