I'll remember that, or at least try to, once I'm using dnf for upgrades. In my case, at least, the main problem other than disk space was google earth conflicting with a filesystem package, and after the upgrade, it still does. And, since I was using the computer at the time, all I had to do was look at the terminal the upgrade was using to see what had gone wrong.
Does this dnf upgrade method leave any record of errors if and when it's not able to complete?