Did my (roughly) monthly system upgrades over the last couple of days. Debian has changed the default Python version for the “python3” command to 3.6. (And Blender now requires that version for building as well.) Didn’t notice anything broken until today, when I tried to print something on my HP inkjet. Turns out the various HP/CUPS-related packages with version number 3.17 want the system default Python to be 3.5, not 3.6. In situations like these, the first thing I have learned to try is to manually download older versions of packages from <http://ftp.debian.org/debian/> and install them with “dpkg -i”. For reference, these are the packages I downgraded: dpkg -i hplip-data_3.16.11+repack0-3_all.deb dpkg -i libhpmud0_3.16.11+repack0-3_amd64.deb dpkg -i libsane-hpaio_3.16.11+repack0-3_amd64.deb dpkg -i printer-driver-hpcups_3.16.11+repack0-3_amd64.deb dpkg -i hplip_3.16.11+repack0-3_amd64.deb And it worked. My printer now prints again. Presumably this will be sorted out in time for my next upgrade ...