Code review comment for lp:~attente/mir/1634508

The unity8 upstart script will never be able to sanitize the environment properly because dbus-update-activation-environment is unable to actually unset MIR_SOCKET after it has been set once (which I guess is why it sets it to "" causing the bug in the first place). You could improve the error message, but there is no other way to prevent this particular problem other than to make the mir client library more robust in its interpretation of MIR_SOCKET.