title: pip: module installed as editable not found
body: <p>I'm trying to install the source checkout of <a href="https://github.com/martok/py-symcircuit" rel="nofollow noreferrer">my own package</a> as an editable package using pip, but it doesn't get picked up as installed.
  Yes, there are a whole lot of related questions, but they're mostly about non-standard directory structures. This here seems like it should &quot;just work&quot; and partially even does.</p>
  <pre><code># starting from an empty venv:
  (env) PS C:\test&gt; pip install -e C:\path\to\my\PySymCircuit
  Obtaining file:///C:/path/to/my/PySymCircuit
    Preparing metadata (setup.py) ... done
  Collecting sympy
    Using cached sympy-1.9-py3-none-any.whl (6.2 MB)
  Collecting mpmath&gt;=0.19
    Using cached mpmath-1.2.1-py3-none-any.whl (532 kB)
  Installing collected packages: mpmath, sympy, SymCircuit
  </code></pre>
  <p>Looks good, but:</p>
  <pre><code>(env) PS C:\test&gt; python -c 'import symcircuit'
  Traceback (most recent call last):
    File &quot;&lt;string&gt;&quot;, line 1, in &lt;module&gt;
  ModuleNotFoundError: No module named 'symcircuit'
  (env) PS C:\test&gt; pip show SymCircuit
  WARNING: Package(s) not found: SymCircuit
  </code></pre>
  <p>The link file that is created is correct (as well as the egg-info in the source directory), and when I try to uninstall the package, suddenly it is recognized. Just not when it matters...</p>
  <pre><code>(env) PS C:\test&gt; cat .\env\Lib\site-packages\SymCircuit.egg-link
  C:\path\to\my\PySymCircuit
  .
  (env) PS C:\test&gt; pip uninstall SymCircuit
  Found existing installation: SymCircuit 0.1.0
  Uninstalling SymCircuit-0.1.0:
    Would remove:
      c:\test\env\lib\site-packages\symcircuit.egg-link
  Proceed (Y/n)? Y
    WARNING: Cannot remove entries from nonexistent file c:\test\env\lib\site-packages\easy-install.pth
    Successfully uninstalled SymCircuit-0.1.0
  </code></pre>
  <p>Plain <code>setup.py develop</code> produces the same link, also not usable.</p>
  <p>What am I missing?</p>
  <p>A non-editable install from the same source tree works as intended, so I believe it has something to do with the linking mechanism?</p>
  <hr />
  <p><strong>Update</strong>: so apparently the link is just for pip, the important part is that setuptools should add the path to <code>easy-install.pth</code>. It doesn't, hence the error message when uninstalling.
  Now the question is, why...</p>
  <hr />
  <p><strong>Update as requested</strong>:</p>
  <p>Local directory structure: <code>git clone https://github.com/martok/py-symcircuit.git</code></p>
  <pre><code>py-symcircuit
  │   LICENSE
  │   README.md
  │   setup.py
  ├───.git
  ├    ...
  ├───symcircuit
  │       __init__.py
  │       bode.py
  │       spice.py
  │       system.py
  └───SymCircuit.egg-info
          dependency_links.txt
          PKG-INFO
          requires.txt
          SOURCES.txt
          top_level.txt
  </code></pre>
  <p>Setup.py:</p>
  <pre><code>#!/usr/bin/env python
  
  from setuptools import setup, find_packages
  
  setup(
      name=&quot;SymCircuit&quot;,
      version=&quot;0.1.0&quot;,
      author=&quot;Martok&quot;,
      author_email=&quot;martok@martoks-place.de&quot;,
      description=&quot;Symbolic electronic circuit analysis&quot;,
      long_description=open(&quot;README.md&quot;,&quot;rt&quot;).read(),
      long_description_content_type=&quot;text/markdown&quot;,
      url=&quot;https://github.com/martok/py-symcircuit&quot;,
      project_urls={
          &quot;Bug Tracker&quot;: &quot;https://github.com/martok/py-symcircuit/issues&quot;,
      },
      license=&quot;MIT&quot;,
      classifiers=[...],
      packages=find_packages(),
      python_requires='&gt;=3.6',
      install_requires=[
          &quot;sympy&quot;,
      ],
      extras_require={
          &quot;EE&quot;: [
              &quot;networkx&quot;,
              &quot;numpy&quot;,
              &quot;mplotkit&quot;
          ],
      },
  )
  </code></pre>
  <pre><code>Python 3.6.8 (tags/v3.6.8:3c6b436a57, Dec 23 2018, 23:31:17) [MSC v.1916 32 bit (Intel)] on win32
  Package          Version  
  ---------------- ---------
  pip              21.3.1
  setuptools       59.4.0
  </code></pre>