title: How to override requiresConstraintBasedLayout in UIView using Swift 3?
body: <p>In the <code>UIView</code>, docs, it is stated that you must override <code>requiresConstraintBasedLayout</code> to return <code>true</code> in your custom view if if needs constraints to work.</p>
  
  <p>How do you do this using Swift 3? </p>