title: pytest make sure your test modules/packages have valid Python names -- can't import
body: <p>I have this file structure.</p>
  <p><a href="https://i.stack.imgur.com/ikvKb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ikvKb.png" alt="enter image description here" /></a></p>
  <p>When ı wrote pytest in my terminal.</p>
  <p>ı have this issue !</p>
  <p><a href="https://i.stack.imgur.com/vaSoT.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vaSoT.png" alt="enter image description here" /></a></p>
  <pre><code>ModuleNotFoundError: No module named 'money_transactions_test'
  Hint: make sure your test modules/packages have valid Python names.
  </code></pre>
  <p>Why its can't import money_transactions_test ?</p>