错误：为仓库 ‘base‘ 下载元数据失败 : Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors

完美解决CentOS8 yum安装AppStream报错 用阿里云的服务器下载宝塔时候出的错，网上的办法普遍不好用，最后在上边的链接给的方案解决了，报错在下面?
Repository extras is listed more than once in the configuration
CentOS-8 - Base - mirrors.aliyun.com 77 B/s | 2.3 kB 00:30
Errors during downloading metadata for repository 'base':
- Status code: 404 for https://mirrors.aliyun.com/centos/8/BaseOS/x86_64/os/repodata/repomd.xml (IP: 42.81.213.230)
- Curl

错误：为仓库 ‘base‘ 下载元数据失败 : Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors最先出现在Python成神之路。