Fix Centos 8 repo due to EOL could not retrieve mirrorlist

If you're getting this error and the repo is failing with Centos 8 with a similar message mentioned below then run the fix script to auto fix the appstream or other repo :

Errors during downloading metadata for repository 'appstream':

  - Curl error (6): Couldn't resolve host name for http://mirrorlist.centos.org/?release=8-stream&arch=x86_64&repo=AppStream&infra=stock [Could not resolve host: mirrorlist.centos.org]

Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: Curl error (6): Couldn't resolve host name for http://mirrorlist.centos.org/?release=8-stream&arch=x86_64&repo=AppStream&infra=stock [Could not resolve host: mirrorlist.centos.org]

Due to EOL the mirrorlist.centos.org doesn't exist anymore and removed you need to change the repo to vault.centos.org

it would help if you ran the below script on your server : 

sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*
sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*
yum update -y