title: Tensorboard not found as magic function in jupyter
body: <p>I want to run tensorboard in jupyter using the latest tensorflow 2.0.0a0. 
  With the tensorboard version 1.13.1, and python 3.6. </p>
  
  <p>using </p>
  
  <p><code>...
  %tensorboard --logdir {logs_base_dir}</code></p>
  
  <p>I get the error :</p>
  
  <p><code>UsageError: Line magic function %tensorboard not found</code></p>
  
  <p>Do you have an idea what the problem could be? It seems that all versions are up to date and the command seems correct too. </p>
  
  <p>Thanks</p>