title: Pytest import error despite using conftest in root directory?
body: <p>I have the following directory structure:</p>
  
  <pre><code>src 
      \conftest.py
      \dir_A
          \run_A.py
          \test_run_A.py
      \dir_B
          \run_B.py
  
  </code></pre>
  
  <p>where run_A.py has the following code:</p>
  
  <pre><code>from dir_B import run_B
  
  ...
  </code></pre>
  
  <p>When I run <code>pytest</code> from <code>src</code>, I get the error:</p>
  
  <pre><code>ImportError while importing test module '/home/user/src/dir_A/run_A.py'
  ...
  
  ImportError: cannot import name 'run_B'
  </code></pre>
  
  <p>Is there a reason why this fails despite using conftest.py?</p>
  
  <p>I'd like to add that running <code>python3 -m dir_A.test_run_A</code> from <code>src</code> works perfectly fine as a test.</p>