title: No active exception to reraise
body: <p>A brief background first.
  I have to run some unit tests. Only issue is that the client wants the failed tests to be reported in form of a word document with some additional information which I can add easily. 
  What I have done till now is this.</p>
  
  <p>I have written a small function which will write stuff in a word document using python-docx. 
  The idea was that I will catch the exception thrown by assertEqual. In the catch block I will call my function to write stuff to word document and then raise the exception again so that old behaviour of a failing unit test is still happening.</p>
  
  <pre><code>class MyTestCase(unittest.TestCase):
      def test_something(self):
          try:
              x = 1
              y = 2
              self.assertEqual(x, y)
          except AssertionError:
              writeToDocument(x, y, self.id().split('.')[-1], 'These values should be equal')
              raise
  
  if __name__ == '__main__':
      unittest.main()
  </code></pre>
  
  <p>At least thats what I thought. I think I am missing something. I see this error when I run the test. This error is raised at the point where I raise the exception after calling my documentation method.</p>
  
  <pre><code>RuntimeError: No active exception to reraise
  </code></pre>
  
  <p>Any ideas where I am messing up on the exception handling stuff?</p>