def _wake(self):
        """
        Wake the multiplexer by writing a byte. If Broker is midway through
        teardown, the FD may already be closed, so ignore EBADF.
        """
        try:
            self.transmit_side.write(b(' '))
        except OSError:
            e = sys.exc_info()[1]
            if e.args[0] != errno.EBADF:
                raise
Wake the multiplexer by writing a byte. If Broker is midway through
        teardown, the FD may already be closed, so ignore EBADF.