title: New auto layout errors with Xcode 8.1
body: <p>I have a macOS app that was running just fine until I upgraded to Xcode 8.1.</p>
  
  <p>The app opens a dialogue with <code>NSOpenPanel</code> to allow the user to choose an image. When I select an image and choose "Open" I get the following error:</p>
  
  <blockquote>
    <p>2016-11-03 10:23:25.589283 PA Places Data[9008:265214] [Layout]
    Detected missing constraints for NSTextField: 0x6000001e3a00.  It
    cannot be placed because there are not enough constraints to fully
    define the size and origin. Add the missing constraints or set
    translatesAutoresizingMaskIntoConstraints=YES and constraints will be
    generated for you. If this view is laid out manually on macOS 10.12
    and later, you may choose to not call [super layout] from your
    override. Set a breakpoint on DETECTED_MISSING_CONSTRAINTS to debug.
    This error will only be logged once.</p>
  </blockquote>
  
  <p>The open dialogue then freezes and cannot be dismissed. </p>
  
  <p>As suggested, I set a breakpoint for <code>DETECTED_MISSING_CONSTRAINTS</code> and find that execution is halting on <code>myPopup.runModal()</code> in this code:</p>
  
  <pre><code>func happyAlert(message: String, info: String) {
      let myPopup: NSAlert = NSAlert()
      myPopup.messageText = message
      myPopup.informativeText = info
      myPopup.alertStyle = NSAlertStyle.informational
      myPopup.addButton(withTitle: "OK")
      myPopup.runModal()
  }
  </code></pre>
  
  <p>This alert informs the user that the image has passed or not passed various validation checks.</p>
  
  <p>What used to happen is that the image was selected, the <code>NSOpenPanel</code> dismissed and the alert appeared without any problems.</p>
  
  <p>Now I get the error about constraints for an NSTextField, but I don't understand why they would be involved here, especially since Xcode does not flag any autolayout issues with the underlying view.</p>
  
  <p>Can anyone explain what might be going on and/or a strategy for further debugging? My experience is limited and I am baffled.</p>