'The outgoing connection attempt was cancelled.  Fail that L{Deferred}
with an L{error.ConnectingCancelledError}.
@param deferred: The L{Deferred <defer.Deferred>} that was cancelled;
should be the same as C{self._onConnection}.
@type deferred: L{Deferred <defer.Deferred>}
@note: This relies on startedConnecting having been called, so it may
seem as though there\'s a race condition where C{_connector} may not
have been set.  However, using public APIs, this condition is
impossible to catch, because a connection API
(C{connectTCP}/C{SSL}/C{UNIX}) is always invoked before a
L{_WrappingFactory}\'s L{Deferred <defer.Deferred>} is returned to
C{connect()}\'s caller.
@return: L{None}'

def _canceller(self, deferred):

    deferred.errback(error.ConnectingCancelledError(self._connector.getDestination()))
    self._connector.stopConnecting()
