'Cleanup client and server connections, and check the error got at
C{connectionLost}.'

def tearDown(self):

    L = []
    for conn in (self.cli, self.svr):
        if (conn.transport is not None):
            d = defer.Deferred().addErrback(_loseAndPass, conn)
            conn.connectionLost = d.errback
            conn.transport.loseConnection()
            L.append(d)
    return defer.gatherResults(L).addErrback((lambda first: first.value.subFailure))
