title: nbformat error trying to open jupyter notebook
body: <p>I am trying to install Jupyter Notebook in macOS Mojave.</p>
  
  <p>I have tryied with Anaconda but although anaconda3 is apparently well installed, with the correct path in my bash, I get: </p>
  
  <pre><code>$ jupyter notebook
  -bash: jupyter: command not found
  </code></pre>
  
  <p>I have also tried with</p>
  
  <p><code>python3 -m pip install --upgrade pip</code></p>
  
  <p><code>python3 -m pip install jupyter</code></p>
  
  <p>but after I try to open <code>jupyter notebook</code> I get this error:</p>
  
  <pre><code>$ jupyter notebook
  Traceback (most recent call last):
    File "/Users/danielavargasrobles/miniconda3/bin/jupyter-notebook", line 7, in &lt;module&gt;
      from notebook.notebookapp import main
    File "/Users/danielavargasrobles/miniconda3/lib/python3.6/site-packages/notebook/notebookapp.py", line 83, in &lt;module&gt;
      from .services.contents.manager import ContentsManager
    File "/Users/danielavargasrobles/miniconda3/lib/python3.6/site-packages/notebook/services/contents/manager.py", line 17, in &lt;module&gt;
      from nbformat import sign, validate as validate_nb, ValidationError
  ModuleNotFoundError: No module named 'nbformat'
  </code></pre>
  
  <p>Does anyone have an idea of what is happening?
  Thank you!</p>