Try removing old kdm.d conf dir created by pre-9.0.0~ if possible

debian/postinst

@@ -4,6 +4,18 @@ set -e
 # Tag to allow some debhelper commands to inject relevant code
 #DEBHELPER#
 
+if [ "${1}" = "configure" ]; then
+    if dpkg --compare-versions ${2} lt "9.0.0"; then
+        # Try remove folder if empty, left after 9.0.0~exp1 conf suppression
+        # by debhelper conffile handling
+        OLD_KDM_DIR=/etc/default/kdm.d
+        if [ -d ${OLD_KDM_DIR} ] ; then
+            echo "Removing old KDM configuration directory \"${OLD_KDM_DIR}\""
+            rmdir ${OLD_KDM_DIR} || true
+        fi
+    fi
+fi
+
 if [[ "$1" = "configure" || "$1" = "abort-upgrade" || "$1" = "abort-remove" ]]; then
     # Theme package alternatives
     while read theme priority; do