title: xcode 8 can't be opened on macOS 10.14
body: <p>I am trying to migrate Swift 2 to Swift 4 but I need to have xcode 8 to do that. My problem is, the latest update on MacOS Mojave 10.14 does not allow me to open the outdated xcode 8. </p>
  
  <p>Anyone know another to convert swift 2 to swift 3 or 4? Or another way to download xcode 8 instead of updating xcode 8 to 10?</p>
  
  <p><a href="https://i.stack.imgur.com/rM1jv.png" rel="noreferrer"><img src="https://i.stack.imgur.com/rM1jv.png" alt="error"></a></p>