Decide what model assertion series to fetch depending on the suite. Use 16 for xenial and 18 for other series (bionic+). This enables core18 image builds.

debian/changelog

@@ -1,3 +1,11 @@
+livecd-rootfs (2.542) UNRELEASED; urgency=medium
+
+  * Decide what model assertion series to fetch depending on the suite. Use 16
+    for xenial and 18 for other series (bionic+). This enables core18 image
+    builds.
+
+ -- Łukasz 'sil2100' Zemczak <lukasz.zemczak@ubuntu.com>  Wed, 03 Oct 2018 11:51:59 +0200
+
 livecd-rootfs (2.541) cosmic; urgency=medium
 
   [ Michael Hudson-Doyle ]

live-build/auto/config

@@ -185,6 +185,14 @@ case $IMAGEFORMAT in
 			*)
 				UBUNTU_IMAGE_ARGS="" ;;
 		esac
+		case $SUITE in
+			xenial)
+				# Ubuntu Core 16
+				;;
+			*)
+				# Ubuntu Core 18
+				MODEL="ubuntu-core-18-${MODEL#pc-}" ;;
+		esac
 
 		echo "IMAGEFORMAT=$IMAGEFORMAT" >> config/common
 		echo "UBUNTU_IMAGE_ARGS=\"$UBUNTU_IMAGE_ARGS\"" >> config/common