title: Android studio Cannot resolve symbol 'NotificationChannel'
body: <p>I have updated Android Studio to 3.0 Beta 5</p>
  
  <p>Other classes like NotificationManager are imported just fine. But it's not finding NotificationChannel anywhere.</p>
  
  <pre><code>import android.app.NotificationChannel;
  </code></pre>
  
  <p>What could cause this?</p>