title: pip install success but ModuleNotFoundError
body: <p>My directory structure is:</p>
  
  <pre><code>package/
    __init__.py
    setup.py
  </code></pre>
  
  <p>setup.py is:</p>
  
  <pre><code>from setuptools import setup, find_packages
  
  setup(
      name="package",
      version="0.0.1",
      packages=find_packages(),
  )
  </code></pre>
  
  <p>When I run <code>pip install ./package</code>, the install successes:</p>
  
  <pre><code>Processing ./package
  Installing collected packages: package
    Running setup.py install for package ... done
  Successfully installed package-0.0.1
  </code></pre>
  
  <p>However, I can't import it:</p>
  
  <pre><code>In [1]: import package
  ---------------------------------------------------------------------------
  ModuleNotFoundError                       Traceback (most recent call last)
  &lt;ipython-input-1-f73d57b147d4&gt; in &lt;module&gt;()
  ----&gt; 1 import package
  
  ModuleNotFoundError: No module named 'package'
  </code></pre>
  
  <p>How to create a package and import it?</p>