title: Python pickle FileNotFound for specific name
body: <p>I have an strange problem trying to save a pickle using Python 3.7.4 on Windows 10. When I use a specific name starting with 'aux', it throws a FileNotFoundError. If I change the name it works great:</p>
  
  <pre><code>import pickle
  
  list_example = [1, 2, 3]
  
  # normal string - breaks
  pickle.dump(list_example, open('aux.pk', 'wb'))
  
  # trying raw string - breaks
  pickle.dump(list_example, open(r'aux.pk', 'wb'))
  
  # trying formatted string - breaks
  file_name = 'aux'
  pickle.dump(list_example, open(f'{file_name}.pk', 'wb'))
  
  # trying other extension - breaks
  pickle.dump(list_example, open('aux.foo', 'wb'))
  
  # changing name, it works
  pickle.dump(list_example, open('tux.pk', 'wb'))
  pickle.dump(list_example, open('tux.foo', 'wb'))
  </code></pre>
  
  <p>I know I can change the name and make it works But, just for the curiosity, does anyone know why it happens?</p>