Write one line of diff information.

def writeInfoLine(self, stream, fromUUID, size):
        """ Write one line of diff information. """
        if size is None or fromUUID is None:
            return
        if not isinstance(size, int):
            logger.warning("Bad size: %s", size)
            return
        stream.write(str("%s\t%s\t%d\n" % (
            self.uuid,
            fromUUID,
            size,
        )))