Snapd for uc20 model assertions does not support global channel overrides.

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.633) UNAPPROVED; urgency=medium
+
+  * Snapd for uc20 model assertions does not support global channel overrides.
+    So make sure --channel is not passed to u-i for any uc20 builds for now.
+
+ -- Łukasz 'sil2100' Zemczak <lukasz.zemczak@ubuntu.com>  Thu, 12 Dec 2019 14:10:37 +0100
+
 livecd-rootfs (2.632) focal; urgency=medium
 
   [ David Krauser ]

live-build/auto/build

@@ -74,9 +74,8 @@ if [ "${IMAGEFORMAT:-}" = "ubuntu-image" ]; then
 	# Use ubuntu-image instead of live-build
 
 	if [ "$PROJECT" = "ubuntu-core" ]; then
-		CHANNEL="${CHANNEL:-edge}"
 		env SNAPPY_STORE_NO_CDN=1 \
-		ubuntu-image snap -c "$CHANNEL" $UBUNTU_IMAGE_ARGS \
+		ubuntu-image snap $UBUNTU_IMAGE_ARGS \
 			-O output "$PREFIX".model-assertion
 		# XXX: currently we only have one image generated, but really
 		#  we should be supporting more than one for models that

live-build/auto/config

@@ -345,6 +345,7 @@ case $IMAGEFORMAT in
 		if [ $PROJECT = "ubuntu-core" ]; then
 			# snap-based core images
 
+			CHANNEL="${CHANNEL:-edge}"
 			case $MODEL in
 				pc-amd64|pc-i386)
 					[ -z "${SUBARCH:-}" ] \
@@ -355,13 +356,19 @@ case $IMAGEFORMAT in
 			case $SUITE in
 				xenial)
 					# Ubuntu Core 16
+					UBUNTU_IMAGE_ARGS="$UBUNTU_IMAGE_ARGS -c $CHANNEL"
 					;;
 				bionic)
 					# Ubuntu Core 18
-					MODEL="ubuntu-core-18-${MODEL#pc-}" ;;
+					MODEL="ubuntu-core-18-${MODEL#pc-}"
+					UBUNTU_IMAGE_ARGS="$UBUNTU_IMAGE_ARGS -c $CHANNEL"
+					;;
 				*)
 					# Ubuntu Core 20
-					MODEL="ubuntu-core-20-${MODEL#pc-}" ;;
+					# XXX: Currently uc20 assertions do not support global
+					#  channel overrides.
+					MODEL="ubuntu-core-20-${MODEL#pc-}"
+					;;
 			esac
 
 			case "$ARCH+${SUBARCH:-}" in