postgres-client-common reports devuan as an unknown version of debian.
The script at fault is /usr/share/postgresql-common/supported-versions, here is a patch that shows the installed version of postgres for devuan jessie. supported-versions.diff
Thanks for your patch! I couldn't find a way to apply it though :/
$/usr/share/postgresql-common# patch --dry-run < supported-versions.diff checking file supported-versions Hunk #1 FAILED at 59. Hunk #2 FAILED at 150. 2 out of 2 hunks FAILED
I made another one, using diff -u: supported-versions.patch