I saw mention of dnf in a blog article about installing a package on CentOS. Further investigation revealed that Fedora is replacing yum with dnf, apparently a new and better yum. But it wasn't clear if dnf was a drop-in replacement or if some migration setup was required. Is it supposed to work with CentOS or do we ignore it until some future release?
https://www.linux.com/learn/what-you-need-know-about-fedoras-switch-yum-dnf
I installed dnf with yum and tried installing another package with it and it complains:
[root@orifice ~]# dnf install certbot Failed to open: /var/cache/dnf/x86_64/7/x86_64/7/epel/repodata/b3221500eaedf45b7ec0737a410cde7e3f09b49070c729449938b961ccbdf397-updateinfo.xml.bz2.
I don't install new packages often, but it does sound like dnf's new dep solver is a Good Thing when that's needed.