You may see errors like the following while perform YUM updates are installs.
https://repo.example.com/yum/release/el7/repodata/repomd.xml: [Errno 14] curl#60 - "Peer's Certificate has expired."
This error indicates that a repositories SSL has expired and YUM can no longer verify it's authenticity. In this example, repo.example.com is the affected repository.
The affected repository will need to be fixed or disabled until such time as the SSL error is no longer occurring. The repository will be located in the /etc/yum.repos.d/ directory and it can be disabled by changing the "enabled=1" lines to "enabled=0".