在使用Yoast_Robot的时候发现一个致命错误 Source model metarobots/product_attribute_source_unit not found for attribute 其实已经删了，后来才发现原来属性没删，core_resource里面也没清理干净...执行如下的SQL语句便可：

DELETE FROM `eav_attribute` WHERE `eav_attribute`.`attribute_code` = 'meta_robots';
DELETE FROM `core_resource` WHERE CODE = 'metarobots_setup';