title: Python Unittest shortDescription printing out None
body: <p>I found out about the <code>shortDescription</code> function and was eager to try it out.</p>
  
  <blockquote>
    <p>shortDescription()
    Returns a description of the test, or None if no description has been provided. The default implementation of this method returns the first line of the test method’s docstring, if available, or None.</p>
  </blockquote>
  
  <p>Strangely enough, I can't get it to work.
  Can anybody spot what I'm doing wrong?</p>
  
  <p>My class does inherit from <code>unittest.TestCase</code> and even it has a docstring</p>
  
  <pre><code>def test_smth(self):
      """
      TEST
      """
      self.description = 'TEST!'
      print(self.shortDescription())
  </code></pre>
  
  <p>Prints out <code>None</code> in Python 3.6</p>