title: versioneer installed, but pip install still gives ModuleNotFoundError
body: <p>I have the <code>versioneer</code> module installed in my environment, as confirmed by running <code>python -m versioneer --version</code>.  Yet when I <code>pip install cartopy</code>, I still get a <code>ModuleNotFoundError</code>, as shown below:</p>
  
  <pre><code>(GIS3) gholl@lce00:~&gt; python -m versioneer --version
  versioneer (installer) 0.18
  (GIS3) gholl@lce00:~&gt; python -V
  Python 3.7.1
  (GIS3) gholl@lce00:~&gt; which python
  /hpc/uhome/gholl/miniconda3/envs/GIS3/bin/python
  (GIS3) gholl@lce00:~&gt; which pip
  /hpc/uhome/gholl/miniconda3/envs/GIS3/bin/pip
  (GIS3) gholl@lce00:~&gt; pip install cartopy
  Collecting cartopy
    Using cached https://files.pythonhosted.org/packages/e5/92/fe8838fa8158931906dfc4f16c5c1436b3dd2daf83592645b179581403ad/Cartopy-0.17.0.tar.gz
    Installing build dependencies ... done
    Getting requirements to build wheel ... error
    Complete output from command /hpc/uhome/gholl/miniconda3/envs/GIS3/bin/python /hpc/uhome/gholl/miniconda3/envs/GIS3/lib/python3.7/site-packages/pip/_vendor/pep517/_in_process.py get_requires_for_build_wheel /hpc/gtmp/gholl/.jtmp.lce00.20190206.082115.24214/tmpmcze3ux9:
    Traceback (most recent call last):
      File "/hpc/uhome/gholl/miniconda3/envs/GIS3/lib/python3.7/site-packages/pip/_vendor/pep517/_in_process.py", line 207, in &lt;module&gt;
        main()
      File "/hpc/uhome/gholl/miniconda3/envs/GIS3/lib/python3.7/site-packages/pip/_vendor/pep517/_in_process.py", line 197, in main
        json_out['return_val'] = hook(**hook_input['kwargs'])
      File "/hpc/uhome/gholl/miniconda3/envs/GIS3/lib/python3.7/site-packages/pip/_vendor/pep517/_in_process.py", line 54, in get_requires_for_build_wheel
        return hook(config_settings)
      File "/lustre1/gtmp/gholl/.jtmp.lce00.20190206.082115.24214/pip-build-env-q2k4jnrs/overlay/lib/python3.7/site-packages/setuptools/build_meta.py", line 130, in get_requires_for_build_wheel
        return self._get_build_requires(config_settings, requirements=['wheel'])
      File "/lustre1/gtmp/gholl/.jtmp.lce00.20190206.082115.24214/pip-build-env-q2k4jnrs/overlay/lib/python3.7/site-packages/setuptools/build_meta.py", line 112, in _get_build_requires
        self.run_setup()
      File "/lustre1/gtmp/gholl/.jtmp.lce00.20190206.082115.24214/pip-build-env-q2k4jnrs/overlay/lib/python3.7/site-packages/setuptools/build_meta.py", line 126, in run_setup
        exec(compile(code, __file__, 'exec'), locals())
      File "setup.py", line 36, in &lt;module&gt;
        import versioneer
    ModuleNotFoundError: No module named 'versioneer'
  
    ----------------------------------------
  Command "/hpc/uhome/gholl/miniconda3/envs/GIS3/bin/python /hpc/uhome/gholl/miniconda3/envs/GIS3/lib/python3.7/site-packages/pip/_vendor/pep517/_in_process.py get_requires_for_build_wheel /hpc/gtmp/gholl/.jtmp.lce00.20190206.082115.24214/tmpmcze3ux9" failed with error code 1 in /lustre1/gtmp/gholl/.jtmp.lce00.20190206.082115.24214/pip-install-2q1hjb0u/cartopy
  </code></pre>
  
  <p>How can it be that the <code>versioneer</code> module is installed but <code>pip install cartopy</code> still fails to find it?</p>
  
  <hr>
  
  <p><sup><em>(I'm aware I <a href="https://stackoverflow.com/a/48168337/974555">should probably not</a> pip install into a conda environment, but I am meanwhile debugging a problem where a complete <code>conda install</code> either wants to downgrade Python, or results in <a href="https://github.com/conda-forge/fiona-feedstock/issues/68" rel="nofollow noreferrer">undefined symbol</a> or <a href="https://github.com/ContinuumIO/anaconda-issues/issues/9449" rel="nofollow noreferrer">cannot open shared object file</a> errors, so this question does have an <a href="https://en.wikipedia.org/wiki/XY_problem" rel="nofollow noreferrer">XY problem</a> aspect to it — however, I still have additional things to try for my Y)</em></sup></p>