Read a single response line from the server.

def _read(self):
        """
        Read a single response line from the server.

        """
        line = ''
        finished = False
        while not finished:
            char = self._socket.recv(1)
            if char == '':
                return ''
            elif char == '\r':
                continue
            elif char == '\n':
                finished = True
                continue
            else:
                line = line + char
        logger.debug('Server sent: ' + line.rstrip())
        return line