title: Error loading Jupyter Notebook Extensions
body: <p>I am using a Macbook with OS Sierra, and running Python 3.6.1 and Jupyter Notebook Server 5.0.0
  I installed Jupyter Notebook extensions, following the instructions as mentioned on <a href="https://github.com/ipython-contrib/jupyter_contrib_nbextensions" rel="noreferrer">https://github.com/ipython-contrib/jupyter_contrib_nbextensions</a></p>
  
  <p>While the notebooks work fine on my system, I cannot view the nbextensions tab. The following is the error log I see on running <code>jupyter notebook</code> in terminal. I have seen some related problems posted here on SO, but they seem to be about installing specific extensions.</p>
  
  <p>Further, one of the solutions seemed to be suggest <code>pip install jupyter_nbextensions_configurator</code>, but as can be seen from the output below, I already have the extension installed.</p>
  
  <pre><code>Requirement already satisfied: traitlets in /usr/local/lib/python3.6/site-packages (from jupyter_nbextensions_configurator)
  Requirement already satisfied: tornado in /usr/local/lib/python3.6/site-packages (from jupyter_nbextensions_configurator)
  </code></pre>
  
  <p>However, in the logs, you will notice that <code>ModuleNotFoundError: No module named 'jupyter_nbextensions_configurator'</code> is one of the error messages.</p>
  
  <pre><code>[W 08:44:49.973 NotebookApp] server_extensions is deprecated, use nbserver_extensions
  [W 08:44:50.146 NotebookApp] Error loading server extension jupyter_nbextensions_configurator
      Traceback (most recent call last):
        File "/usr/local/lib/python3.6/site-packages/notebook/notebookapp.py", line 1271, in init_server_extensions
          mod = importlib.import_module(modulename)
        File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/importlib/__init__.py", line 126, in import_module
          return _bootstrap._gcd_import(name[level:], package, level)
        File "&lt;frozen importlib._bootstrap&gt;", line 978, in _gcd_import
        File "&lt;frozen importlib._bootstrap&gt;", line 961, in _find_and_load
        File "&lt;frozen importlib._bootstrap&gt;", line 948, in _find_and_load_unlocked
      ModuleNotFoundError: No module named 'jupyter_nbextensions_configurator'
  [I 08:44:50.158 NotebookApp] Serving notebooks from local directory: /Users/sp
  [I 08:44:50.158 NotebookApp] 0 active kernels
  [I 08:44:50.158 NotebookApp] The Jupyter Notebook is running at: http://localhost:8888/?token=c777a7ab5dc6cf416c238b7b37f58d10ebea9db0743b46ae
  [I 08:44:50.158 NotebookApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
  [C 08:44:50.163 NotebookApp]
  
      Copy/paste this URL into your browser when you connect for the first time,
      to login with a token:
          http://localhost:8888/?token=c777a7ab5dc6cf416c238b7b37f58d10ebea9db0743b46ae
  [I 08:44:51.633 NotebookApp] Accepting one-time-token-authenticated connection from ::1
  [W 08:44:54.407 NotebookApp] 404 GET /nbextensions/nbextensions_configurator/tree_tab/main.js?v=20170511084449 (::1) 25.76ms referer=http://localhost:8888/tree
  </code></pre>
  
  <p>What am I missing here? Thanks!</p>