Make function raise KnownFailureTest exception if given condition is true.
If the condition is a callable, it is used at runtime to dynamically make the decision. This is useful for tests that may require costly imports, to delay the cost until the test suite is actually executed.
fail_condition : bool or callable
msg : str, optional
decorator : function
The decorator itself is decorated with the nose.tools.make_decorator function in order to transmit function name, and various other metadata.