title: Setup.py duplicates sub packages as separate one
body: <p>I have a following project structure:</p>
  <pre class="lang-none prettyprint-override"><code>.
  └── Project/
      ├── package_1/
      │   ├── package_2
      │   ├── __init__.py
      │   ├── file_1.py
      │   ├── file_2.py
      │   └── file_3.py
      └── __init__.py
  </code></pre>
  <p>As the <code>package_2</code> contains the ported files from another project, I want to be able to install <code>package_1</code> using <code>setuptools</code> so that it doesn't conflict with the original project and import it like this :</p>
  <pre><code>import package_1.package_2
  </code></pre>
  <p>here is my setup.py file content :</p>
  <pre><code>setup(
      name=&quot;Project&quot;,
      ...
      packages=find_packages(exclude=[&quot;package_1&quot;]),
  )
  </code></pre>
  <p>So far everything works perfectly except that in <code>\Lib\site-packages</code> directory in addition to
  <code>package_1/package_2</code> I also have the <code>package_2</code> as a separate module which I think it is not OK.</p>