add ubuntu-mate to the set of projects we add snap model assertions to.

debian/changelog

@@ -4,6 +4,7 @@ livecd-rootfs (2.465) UNRELEASED; urgency=medium
     favor of the generic-classic assertion from the store.
   * move snap assertion handling into the generic build script (and, in
     the process, from the subiquity overlay to the base squashfs).
+  * add ubuntu-mate to the set of projects we add snap model assertions to.
 
  -- Steve Langasek <steve.langasek@ubuntu.com>  Tue, 03 Oct 2017 15:31:21 -0700
 

live-build/auto/build

@@ -298,7 +298,7 @@ deb file:/var/lib/preinstalled-pool/ $LB_DISTRIBUTION $LB_PARENT_ARCHIVE_AREAS
 		rm chroot/etc/apt/sources.list.preinstall chroot/etc/apt/sources.list.orig
 	fi
 	case $PROJECT:$SUBPROJECT in
-		ubuntu-server:live)
+		ubuntu-server:live|ubuntu-mate:*)
 			assertions_dir="chroot/var/lib/snapd/seed/assertions"
 			model_assertion="$assertions_dir/generic-classic.model"
 			account_key_assertion="$assertions_dir/generic.account-key"