title: tensorflow.keras can't import Activation
body: <p>just installed tensorflow-gpu via:</p>
  
  <p><code>conda install --yes tensorflow-gpu==1.12.0</code></p>
  
  <p>Now when I run <code>from tensorflow.keras import layers</code> into the error:</p>
  
  <blockquote>
    <p>ImportError: cannot import name 'Activation'</p>
  </blockquote>
  
  <p>I tried removing tf and keras then reinstalling tf, but hasn't helped.</p>