YumRepo Error: All mirror URLs are not using ftp, http[s] or file. (CentOS 6)

# yum install -y libffi-devel
Loaded plugins: fastestmirror, security
Setting up Install Process
Loading mirror speeds from cached hostfile
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
 Eg. Invalid release/repo/arch combination/
removing mirrorlist with no valid mirrors: /var/cache/yum/x86_64/6/base/mirrorlist.txt
Error: Cannot find a valid baseurl for repo: base

echo https://vault.centos.org/6.10/os/x86_64/ > /var/cache/yum/x86_64/6/base/mirrorlist.txt
echo http://vault.centos.org/6.10/extras/x86_64/ > /var/cache/yum/x86_64/6/extras/mirrorlist.txt
echo http://vault.centos.org/6.10/updates/x86_64/ > /var/cache/yum/x86_64/6/updates/mirrorlist.txt