One problem is that certbot-auto is going to erase plugins that you install with pip this way.
As you can see at https://certbot.eff.org/ if you select your operating system versn, on your OS we recommend using a Certbot Docker image if you need DNS plugins.
https://certbot.eff.org/docs/install.html#running-with-docker
If this isn't a good option for you, you might want to upgrade to CentOS 7, as indicated by @mnordhoff, or try acme.sh: