title: str object is not callable for unittest
body: <p>I have written a test case which shows the error</p>
  
  <pre><code>from unittest import *
  class MyTest(unittest.TestCase):
      def test_add(self):
          self.assertEquals(1,(2-1),"Sample Subraction Test")
  
  
  if __name__ == '__main__':
      unittest.main()
  </code></pre>
  
  <p>Output:
  Str object is not callable</p>
  
  <p>Instead of 
  "from unittest import *" I have given 
  "import unittest"</p>
  
  <p>it worked</p>
  
  <p>but still i couldn't get point it accurately 
  what might be the reason for this?</p>