def addExpectedFailure(test, failure, todo=None):
        """
        Record that the given test failed, and was expected to do so.

        In Twisted 15.5 and prior, C{todo} was a mandatory parameter.

        @type test: L{unittest.TestCase}
        @param test: The test which this is about.
        @type error: L{failure.Failure}
        @param error: The error which this test failed with.
        @type todo: L{unittest.Todo}
        @param todo: The reason for the test's TODO status. If L{None}, a
            generic reason is used.
        """

        Record that the given test failed, and was expected to do so.

        In Twisted 15.5 and prior, C{todo} was a mandatory parameter.

        @type test: L{unittest.TestCase}
        @param test: The test which this is about.
        @type error: L{failure.Failure}
        @param error: The error which this test failed with.
        @type todo: L{unittest.Todo}
        @param todo: The reason for the test's TODO status. If L{None}, a
            generic reason is used.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/itrial.py