title: Recursive unittest discovery with python3 and without __init__.py files
body: <p>I have project with the following directory structure:</p>
  
  <pre><code>.
  ├── requirements.txt
  ├── main.py
  ├── tests
      ├── unit
      │   └── test_thing1.py
      │   └── test_thing2.py
      └── integration
          └── test_integration_thing1.py
          └── test_integration_thing2.py
  </code></pre>
  
  <p><strong>I want to run all tests with one command</strong>. If I do <code>python -m unittest discover</code>, no tests are executed. </p>
  
  <p>I found <a href="https://stackoverflow.com/questions/29713541/recursive-unittest-discover">this question</a> that suggest adding a <code>__init__.py</code> file to make packages out of the <code>unit</code> and <code>integration</code> folders. The solution works, and all tests are running this way. </p>
  
  <p>But since I'm using python3 and <code>__init__.py</code> files are not required with <a href="https://www.python.org/dev/peps/pep-0420/" rel="noreferrer">implicit namespace packages</a>, I was wondering if there was a way to make this works without those <code>__init__.py</code> files.</p>