How to fix K3b being "unable to find dvd+rw-format executable" in Debian10?

When starting K3b in Debian10/KDE (at version 18.08 there) I get this error: > Unable to find dvd+rw-format executable > K3b uses dvd+rw-format to format DVD-RWs and DVD+RWs. > Solution: Install the dvd+rw-tools package. The dvd+rw-tools is installed. I have found some very old reports of this from 2004 and 2008 so I thought it got fixed by now. How to fix this problem? I also had this error when trying to burn to a DVD: "Could not determine size of resulting image file." and: > mkisofs > \----------------------- >/usr/bin/genisoimage: Missing pathspec. >Usage: genisoimage [options] -o file directory ... in the debugging ouput. I solved this by making more space available for the /tmp directory. (It didn't say that there was too little disk space in the errors and I didn't get notified about disk space running out there.)