I've been able to recreate this during a distribution upgrade from 16.04 to 18.04 (directory permissions switched from 775 to 777) when the package is unpacked but not yet configured. This could end up causing an issue at a conffile prompt for a different package if your screen session (which the release upgrader runs under) was disconnected.
I've been able to recreate this during a distribution upgrade from 16.04 to 18.04 (directory permissions switched from 775 to 777) when the package is unpacked but not yet configured. This could end up causing an issue at a conffile prompt for a different package if your screen session (which the release upgrader runs under) was disconnected.