title: Getting Python error, "TypeError: 'NoneType' object is not callable" SOMETIMES
body: <p>Not very new to programming or to python but incredibly green to using pyunit. Need to use it for my new job and I keep getting this error but only sometimes when it is run. My code below.</p>
  
  <pre><code>import unittest
  
  from nose_parameterized import parameterized
  from CheckFromFile import listFileCheck, RepresentsFloat
  
  testParams = listFileCheck()
  
  
  class TestSequence(unittest.TestCase):
  
      @parameterized.expand(testParams)
      def test_sequence(self, name, a, b):
          if RepresentsFloat(a):
              self.assertAlmostEqual(a,b,2)
          else:
              self.assertEqual(a,b)
  
  
  if __name__ == '__main__':
      unittest.main()
  </code></pre>
  
  <p>What is happening here is that my test case is pulling a method <em>listFileCheck</em> from another class. What it does is it reads values from the serial port <em>communicating with the control board</em> and compares them with a calibration file. It puts the control board values in an MD array along with the calibration file values. These values can be either str, int, or float.</p>
  
  <p>I used the test case to compare the values to one another however I keep getting this error but only sometimes. After every 3rd or so run it fails with this error.</p>
  
  <pre><code>Error
  Traceback (most recent call last):
    File "C:\Python34\lib\unittest\case.py", line 57, in testPartExecutor
      yield
    File "C:\Python34\lib\unittest\case.py", line 574, in run
      testMethod()
  TypeError: 'NoneType' object is not callable
  
  
  Process finished with exit code 0 
  </code></pre>
  
  <p>Anyone know why I might be getting this error on occasion?</p>