title: Installing package with pip doesn't appear in pip list
body: <p>I'm having issues installing any python package into my pipenv on macOS 10.14.4. I've been using a pipenv with openCV for some time now, but I need sklearn and pandas. I can install them with pip, which succeeds. But when I then try <code>pip list</code>, the packages don't appear. </p>
  
  <p>I've tried installing it in two ways, the first one how I always do it:</p>
  
  <pre><code>(assignments-0VzU3jlg) ~/Doc/2018/A/com/a $ pip install pandas
  Collecting pandas
    Using cached https://files.pythonhosted.org/packages/fc/43/fd867e3347559845c8f993059d410c50a1e18709f1c4d4b3b47323a06a37/pandas-0.24.2-cp37-cp37m-macosx_10_6_intel.macosx_10_9_intel.macosx_10_9_x86_64.macosx_10_10_intel.macosx_10_10_x86_64.whl
  Requirement already satisfied: numpy&gt;=1.12.0 in /Users/pieterdelobelle/.local/share/virtualenvs/assignments-0VzU3jlg/lib/python3.7/site-packages (from pandas) (1.16.2)
  Collecting python-dateutil&gt;=2.5.0 (from pandas)
    Using cached https://files.pythonhosted.org/packages/41/17/c62faccbfbd163c7f57f3844689e3a78bae1f403648a6afb1d0866d87fbb/python_dateutil-2.8.0-py2.py3-none-any.whl
  Collecting pytz&gt;=2011k (from pandas)
    Using cached https://files.pythonhosted.org/packages/61/28/1d3920e4d1d50b19bc5d24398a7cd85cc7b9a75a490570d5a30c57622d34/pytz-2018.9-py2.py3-none-any.whl
  Collecting six&gt;=1.5 (from python-dateutil&gt;=2.5.0-&gt;pandas)
    Using cached https://files.pythonhosted.org/packages/73/fb/00a976f728d0d1fecfe898238ce23f502a721c0ac0ecfedb80e0d88c64e9/six-1.12.0-py2.py3-none-any.whl
  Installing collected packages: six, python-dateutil, pytz, pandas
  Successfully installed pandas-0.24.2 python-dateutil-2.8.0 pytz-2018.9 six-1.12.0
  </code></pre>
  
  <p>But it's not in <code>pip list</code>, and the import in python also fails.</p>
  
  <pre><code>(assignments-0VzU3jlg) ~/Doc/2018/A/com/a $ pip list
  Package       Version 
  ------------- --------
  numpy         1.16.2  
  opencv-python 4.0.0.21
  pip           19.0.3  
  setuptools    40.8.0  
  wheel         0.33.1  
  </code></pre>
  
  <p>Now, since that $PATH might be messed up, I've tried calling that pip directly, as shown below. But the issue is still exactly the same. </p>
  
  <pre><code> ~/Doc/2018/A/com/a $ /Users/pieter/.local/share/virtualenvs/assignments-0VzU3jlg/bin/pip install pandas
  Collecting pandas
    Using cached https://files.pythonhosted.org/packages/fc/43/fd867e3347559845c8f993059d410c50a1e18709f1c4d4b3b47323a06a37/pandas-0.24.2-cp37-cp37m-macosx_10_6_intel.macosx_10_9_intel.macosx_10_9_x86_64.macosx_10_10_intel.macosx_10_10_x86_64.whl
  Collecting pytz&gt;=2011k (from pandas)
    Using cached https://files.pythonhosted.org/packages/61/28/1d3920e4d1d50b19bc5d24398a7cd85cc7b9a75a490570d5a30c57622d34/pytz-2018.9-py2.py3-none-any.whl
  Collecting python-dateutil&gt;=2.5.0 (from pandas)
    Using cached https://files.pythonhosted.org/packages/41/17/c62faccbfbd163c7f57f3844689e3a78bae1f403648a6afb1d0866d87fbb/python_dateutil-2.8.0-py2.py3-none-any.whl
  Requirement already satisfied: numpy&gt;=1.12.0 in /Users/pieterdelobelle/.local/share/virtualenvs/assignments-0VzU3jlg/lib/python3.7/site-packages (from pandas) (1.16.2)
  Collecting six&gt;=1.5 (from python-dateutil&gt;=2.5.0-&gt;pandas)
    Using cached https://files.pythonhosted.org/packages/73/fb/00a976f728d0d1fecfe898238ce23f502a721c0ac0ecfedb80e0d88c64e9/six-1.12.0-py2.py3-none-any.whl
  Installing collected packages: pytz, six, python-dateutil, pandas
  Successfully installed pandas-0.24.2 python-dateutil-2.8.0 pytz-2018.9 six-1.12.0
  </code></pre>
  
  <pre><code>~/Doc/2018/A/com/a $ /Users/pieter/.local/share/virtualenvs/assignments-0VzU3jlg/bin/pip list
  Package       Version 
  ------------- --------
  numpy         1.16.2  
  opencv-python 4.0.0.21
  pip           19.0.3  
  setuptools    40.8.0  
  wheel         0.33.1  
  </code></pre>
  
  <p>Now, I've had some issues installing openCV correctly in the virtualenv, so I might have done something to mess this up. But I don't understand how this—and especially the second try—can't correctly install the packages...</p>
  
  <p>For reference, I'm using <code>pip 19.0.3</code>:</p>
  
  <pre><code>~/Doc/2018/A/com/a $ /Users/pieter/.local/share/virtualenvs/assignments-0VzU3jlg/bin/pip --version 
  pip 19.0.3 from /Users/pieter/.local/share/virtualenvs/assignments-0VzU3jlg/lib/python3.7/site-packages/pip (python 3.7)
  </code></pre>
  
  <p><strong>edit</strong>
  I'm using pipenv. The <code>pipenv install pandas</code> command adds pandas to the pipfile, but doesn't allow me to use it, not even in a shell (<code>pipenv shell</code>) afterwards. </p>
  
  <pre><code> ~/Doc/2018/A/com/a $ pipenv install pandas
  Installing pandas…
  ✔ Installation Succeeded 
  Installing dependencies from Pipfile.lock (caa119)…
       ▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉ 12/12 — 00:00:08
  To activate this project's virtualenv, run pipenv shell.
  Alternatively, run a command inside the virtualenv with pipenv run.
  </code></pre>
  
  <pre><code> ~/Doc/2018/A/com/a $ pipenv run python -c "import pandas as pd"
  Traceback (most recent call last):
    File "&lt;string&gt;", line 1, in &lt;module&gt;
  ModuleNotFoundError: No module named 'pandas'
  </code></pre>