title: Make setup.py from subdirectory prefix imports with broader namespace?
body: <p>I'm using Python 3.7 and I have a directory structure that looks like this:</p>
  
  <pre><code>a
    b
      __init__.py
      c.py
      setup.py
  </code></pre>
  
  <p>I'd like to construct a <code>setup.py</code> that will allow me to run <code>pip install -e .</code> from within the <code>b</code> subdirectory and then be able to do:</p>
  
  <pre><code>from a.b import c
  </code></pre>
  
  <p>I've been struggling with this for hours (trying various sets of arguments to <code>find_packages</code> and <code>find_namespace_packages</code>) and I haven't been able to figure out a way to make this work — I think I have a fundamental misunderstanding of setuptools. Any advice would be appreciated — thanks!</p>