@abc.abstractmethod<EOL><INDENT>@asyncio.coroutine<EOL>def abort(self):<DEDENT>
Abort the authentication. The result is either the failure tuple
(``(SASLState.FAILURE, None)``) or a :class:`SASLFailure` exception if
the response from the peer did not indicate abortion (e.g. another
error was returned by the peer or the peer indicated success).