title: Coverage python library not found after installing
body: <p>I ran the command pip install coverage and it appears to have installed correctly.</p>
  
  <pre><code>Frodo:Triangle567 tarikkdiry$ pip install coverage
      Collecting coverage
        Using cached https://files.pythonhosted.org/packages/c7/d0/337673c08f5b0cc7ada3dfe2a998ae8a97d482722045644be3d79bbcbe05/coverage-4.5.1-cp37-cp37m-macosx_10_13_x86_64.whl
      Installing collected packages: coverage
      Successfully installed coverage-4.5.1
  </code></pre>
  
  <p>However, after running coverage on one of my test files, I receive this error:</p>
  
  <pre><code>Frodo:Triangle567 tarikkdiry$ coverage run testtriangle.py
  Traceback (most recent call last):
    File "/Library/Frameworks/Python.framework/Versions/3.7/bin/coverage", line 7, in &lt;module&gt;
      from coverage.cmdline import main
  ModuleNotFoundError: No module named 'coverage.cmdline'; 'coverage' is not a package
  Frodo:Triangle567 tarikkdiry$
  </code></pre>
  
  <p>I have tried uninstalling every python package and reinstalling but to no success. I have tried this on another machine and can confirm the test file is working properly.</p>
  
  <p>EDIT: After running pip3 check coverage and pip3 show coverage</p>
  
  <p>pip3 check coverage:</p>
  
  <pre><code>No broken requirements found.
  </code></pre>
  
  <p>pip3 show coverage</p>
  
  <pre><code>Name: coverage
  Version: 4.5.1
  Summary: Code coverage measurement for Python
  Home-page: https://bitbucket.org/ned/coveragepy
  Author: Ned Batchelder and 100 others
  Author-email: ned@nedbatchelder.com
  License: Apache 2.0
  Location: /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages
  Requires:
  Required-by:
  </code></pre>