title: Failed to resolve: firebase-database-15.0.0
body: <p>connecting firebase real-time database with assistant
  when adding the dependencies of firebase database this error is showing:</p>
  
  <pre><code>Failed to resolve: firebase-database-15.0.0
  </code></pre>
  
  <p>this also happened with authentication</p>
  
  <p>My android studio version 3.2 build September 18</p>
  
  <p><a href="https://i.stack.imgur.com/cg0QT.png" rel="noreferrer"><img src="https://i.stack.imgur.com/cg0QT.png" alt="enter image description here"></a> </p>