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
It looks, from the server traceback, as though you've potentially got something weird going on with multiple python installs. Note that you're installing into a python in
/usr/local/lib/python3.6
but your notebook server traceback goes from there (where notebookapp seems to be running), but crosses over (in the importing call) to running from a (homebrew?) Python installed at
/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6
A potentially hackish solution might be to just install into that cellar, and carry on as before, but I'd suggest maybe a little more investigation to decide why this is happening. Of relevance may be how you start the notebook server, install modules, run terminals, setup python paths, etc...