'Send a POP3 command to which a short response is expected.
Block all further commands from being sent until the response is
received.  Transition the state to SHORT.
@type cmd: L{bytes}
@param cmd: A POP3 command.
@type args: L{bytes}
@param args: The command arguments.
@rtype: L{Deferred <defer.Deferred>} which successfully fires with
L{bytes} or fails with L{ServerErrorResponse}
@return: A deferred which fires when the entire response is received.
On an OK response, it returns the response from the server minus
the status indicator.  On an ERR response, it issues a server
error response failure with the response from the server minus the
status indicator.'

def sendShort(self, cmd, args):

    d = self._blocked(self.sendShort, cmd, args)
    if (d is not None):
        return d
    if args:
        self.sendLine(((cmd + '    ') + args))
    else:
        self.sendLine(cmd)
    self.state = 'SHORT'
    self._waiting = defer.Deferred()
    return self._waiting
