First of all we have to troubleshoot the issues, as it can reveal some more information and at least it gives more knowledge.
This issue is caused by some problem in a repository called epel (extra packages from enterprise linux). It has something to do with expired ca-certificates. When surfing internet you can find some suggestions and workarounds. below workaround and fix worked for me...
This can be skipped by modifying the epel repe configuration. use text editor (vi,vim, nano etc) to edit /etc/yum.repos.d/epel.repo
Then edit 4th line, change https to http.(red underlined in below image) and save
Then you would be able to do normal yum operations.
For permanent fix, you can update the repos after this, and then revert the changes. as https is way better than http.
If you have any question regarding this, contact me. or google it.