Changed TestTraceback.test_traceback_verbiage to use test.support and test.script_helper (much simpler now, thanks Antoine!).

It is still in test_raise, however.  

I do not understand why we would put it in test_cmd_line_script -- it seems to me that test_cmd_line_script is to verify that python is working correctly when executing scripts, but for this test we are assuming that python does work correctly when executing scripts and we testing the verbiage from raising exceptions.