title: Getting a "This application is modifying the autolayout engine from a background thread" error?
body: <p>Been encountering this error a lot in my OS X using swift: </p>
  
  <blockquote>
    <p>"This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes.  This will cause an exception in a future release."</p>
  </blockquote>
  
  <p>I have a my <strong>NSWindow</strong> and I'm swapping in views to the <code>contentView</code> of the window. I get the <strong>error</strong> when I try and do a <code>NSApp.beginSheet</code> on the window, or when I add a <code>subview</code> to the window. Tried disabling autoresize stuff, and I don't have anything using auto layout. Any thoughts?</p>
  
  <p>Sometimes it's fine and nothing happens, other times it totally breaks my <code>UI</code> and nothing loads</p>