title: Python setuptools get IOError not a directory for json file
body: <p>I am learning to write the setup.py for a python package that I am developing. I have a couple of json and yaml files in this package and in the setup.py file I added</p>
  
  <pre><code>    package_data={"tiny.core": ["*.json"],
                    "tiny.vasp_io": ["*.yaml"]},
  </code></pre>
  
  <p>I also added the following info in the MANIFEST.in file:</p>
  
  <pre><code>include *.rst requirements*.txt
  recursive-include tiny *.py *.json *.yaml
  </code></pre>
  
  <p>and the following in the setup.cfg file</p>
  
  <pre><code>[aliases]
  release = register sdist bdist_wheel upload
  </code></pre>
  
  <p>Then I did <code>python setup.py install</code> and everything looked fine. But when I ran my package, I got <code>IOError: [Errno 20] Not a directory</code> for a json file in the egg. However, when I unzipped the egg folder, the json was in there. If I deleted the egg file, everything went back to normal again. I am pretty new to setuptools. Any ideas why this is happening? I also noticed that some other python modules have egg-link file, but I don't have that. Is that the reason here?
  The repository takes this kind of shape:</p>
  
  <pre><code>/tiny
  - .git/
  - setup.py
  - setup.cfg
  - requirements.txt
  - MANIFEST.in
  - README.rst
  - tiny
      - __init__.py
      - core
          - __init__.py
          - json_files.json
          - yaml_files.yaml
          - some_script.py
      - cli
          - __init__.py
          - cli.py
          - some_script.py
  </code></pre>
  
  <p>It seems if I use <code>python setup.py develop</code>, I won't get the error. Not really sure why.</p>