dbus supports policy files in both /usr/share/dbus-1/system.d and
/etc/dbus-1/systemd. [The] recently released dbus 1.14.0, officially
deprecates installing packages' default policies into /etc/dbus-1/systemd,
instead reserving it for the sysadmin. This is the same idea as the
difference between /usr/lib/udev/rules.d and /etc/udev/rules.d.
From https://bugs.debian.org/1006631: