title: Adding a GitHub repository in Xcode 7 using SSH authentication gives an authentication error
body: <p>I'm trying to set up a Bot in Xcode 7 for integration testing.  As part of setting this up I am adding a remote repository to the project using <em>Xcode > Preferences > Accounts > Add Repository...</em> but it fails with the message <em>Authentication failed</em>:  </p>
  
  <p><a href="https://i.stack.imgur.com/V4u9p.png" rel="noreferrer"><img src="https://i.stack.imgur.com/V4u9p.png" alt="enter image description here"></a></p>
  
  <p>GitHub is working at the command line using this SSH key, why is Xcode 7 not working?</p>