Fix the test to expect a string that properly names TypeError.

Python 2 and Python 3 have different ideas about what the proper name of TypeError is.


git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/branches/assertraises-py3-7534@43063 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb