title: Python: "No module named 'requests' " after pip3 install requests in pipenv
body: <p>I'm trying to install the library requests in pipenv, with Python 3.  I've tried:</p>
  
  <ol>
  <li><code>pip install requests</code>, before forgetting that <code>pip</code> installs only for Python 2, leading to,</li>
  <li><code>pip3 install requests</code>, which returns assuringly</li>
  </ol>
  
  <hr>
  
  <pre><code>Requirement already satisfied: requests in /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages (2.19.1)
  Requirement already satisfied: idna&lt;2.8,&gt;=2.5 in /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages (from requests) (2.7)
  Requirement already satisfied: urllib3&lt;1.24,&gt;=1.21.1 in /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages (from requests) (1.23)
  Requirement already satisfied: certifi&gt;=2017.4.17 in /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages (from requests) (2018.8.24)
  Requirement already satisfied: chardet&lt;3.1.0,&gt;=3.0.2 in /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages (from requests) (3.0.4)
  </code></pre>
  
  <p>When I run my python files with <code>import requests</code>, everything works, but when I run <code>pipenv run python mypythonscript.py</code>, I get the error <code>ModuleNotFoundError: No module named 'requests'</code>. Please advise what I'm missing.</p>