title: Facebook SDK '4.+' suddenly throws import error, things glow in red - Android Studio (2.0)
body: <p>While testing my app, I had no problems with the Facebook SDK. Suddenly today, every Facebook imports are glowing in red.</p>
  
  <p>I have cleared my project, rebuilt it several times, restarted Android Studio but nothing has changed.</p>
  
  <p>What should I do?</p>
  
  <p>Thanks!</p>
  
  <p><a href="https://i.stack.imgur.com/mL5gt.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/mL5gt.png" alt="enter image description here"></a></p>