title: Pipenv not setting PYTHONPATH
body: <p>I have the following structure</p>
  
  <pre><code>.
  ├── module1
  │   ├── __init__.py
  │   └── start.py
  ├── module2
  │   ├── __init__.py
  │   └── settings.py
  └── Pipfile
  </code></pre>
  
  <p>cat module1/start.py </p>
  
  <pre><code>from module2.settings import VAR
  
  if __name__ == '__main__':
      print(VAR)
  </code></pre>
  
  <p>cat module2/settings.py </p>
  
  <pre><code>VAR = 'foo'
  </code></pre>
  
  <p>If I try to run my program I get </p>
  
  <pre><code>pipenv shell
  python module1/start.py
  
  Traceback (most recent call last):
    File "module1/start.py", line 1, in &lt;module&gt;
      from module2.settings import VAR
  ModuleNotFoundError: No module named 'module2'
  </code></pre>
  
  <p>or </p>
  
  <pre><code>pipenv run python module1/start.py
  
  Traceback (most recent call last):
    File "module1/start.py", line 1, in &lt;module&gt;
      from module2.settings import VAR
  ModuleNotFoundError: No module named 'module2'
  </code></pre>
  
  <p>Why doesn't pipenv set PYTHONPATH correctly ?</p>