def test_failureElementValue(self):
        """
        The I{value} renderer of L{FailureElement} renders the value's exception
        value.
        """
        element = FailureElement(
            self.failure, TagLoader(tags.span(render="value")))
        d = flattenString(None, element)
        d.addCallback(
            self.assertEqual, b'<span>This is a problem</span>')
        return d

        The I{value} renderer of L{FailureElement} renders the value's exception
        value.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_util.py