def find(self,regex):
        try:
            tc.go(self.url)
            tc.find(regex) 
        except TwillAssertionError:
            self.fail("No match to '%s' on %s" % (regex, self.url))
By default Twill commands throw exceptions rather than failures when 
dataset/ETHPy150Open garethr/django-test-extensions/src/test_extensions/twill.py/TwillCommon.find