title: How to *install* extra package data using setuptools?
body: <p>This looks an awful lot like <a href="https://stackoverflow.com/questions/7522250/how-to-include-package-data-with-setuptools-distribute">this question</a>, but it isn't quite.</p>
  
  <p>The answers to that question cover how to get extra data into a source distribution and binary distribution, but don't actually address how to get package data <em>installed</em> when included in a source distribution, or how to get them installed in a wheel file.</p>
  
  <p>Here's an example of what I mean (python 3.7.4):</p>
  
  <pre><code>% ls
  MANIFEST.in README.txt  foopackage  setup.py    venv
  
  % cat setup.py
  # -*- coding: utf-8 -*-
  
  from setuptools import setup, find_packages
  
  setup(
      name='foopackage',
      version='0.0.1',
      description='A Package Full of Foo',
      packages=find_packages(),
      package_data={
          'foopackage': [
              'README.txt',
          ],
      },
      include_package_data=True,
  )
  
  % cat MANIFEST.in
  include README.txt
  
  % . venv/bin/activate
  (venv)
  % python setup.py sdist bdist_wheel
  [...]
  % ls dist
  foopackage-0.0.1-py3-none-any.whl foopackage-0.0.1.tar.gz
  (venv)
  % unzip -v dist/foopackage-0.0.1-py3-none-any.whl| grep README.txt
  (venv)
  % tar tvzf dist/foopackage-0.0.1.tar.gz| grep README.txt
  -rw-r--r--  0 matt   staff       0  8 Nov 17:21 foopackage-0.0.1/README.txt
  (venv)
  % deactivate
  
  % cd ../foo
  
  % . py/bin/activate
  (py)
  % pip install ../foopackage/dist/foopackage-0.0.1.tar.gz
  Processing ../foopackage/dist/foopackage-0.0.1.tar.gz
  Installing collected packages: foopackage
    Found existing installation: foopackage 0.0.1
      Uninstalling foopackage-0.0.1:
        Successfully uninstalled foopackage-0.0.1
    Running setup.py install for foopackage ... done
  Successfully installed foopackage-0.0.1
  You are using pip version 19.0.3, however version 19.3.1 is available.
  You should consider upgrading via the 'pip install --upgrade pip' command.
  (py)
  % find . -name README.txt
  (py)
  %
  </code></pre>
  
  <p>The <code>README.txt</code> file isn't included in the <code>wheel</code>, and despite being included in the <code>sdist</code> file, it is not installed when that package is installed.</p>
  
  <p>I can't seem to find the magic incantation to get setuptools to actually install this file somewhere.  What am I missing?</p>
  
  <p>I should probably point out that the real package I'm building has to be py27 and py34+ compatible, in case that constrains the solution in any way.</p>