new: catch error earlier. !minor

bin/compose

@@ -747,7 +747,10 @@ _get_docker_compose_service_mixin() {
         return 0
     fi
 
-    master_charm=$(get_top_master_charm_for_service "$service") || return 1
+    master_charm=$(get_top_master_charm_for_service "$service") || {
+        err "Failed to get top master charm for service $DARKYELLOW$service$NORMAL"
+        return 1
+    }
 
     ## The compose part
 
@@ -794,7 +797,10 @@ get_docker_compose () {
     debug "Compiling 'docker-compose.yml' base for $DARKYELLOW$@$NORMAL..."
     for target_service in "$@"; do
         start=$SECONDS
-        services=$(get_ordered_service_dependencies "$target_service") || return 1
+        services=$(get_ordered_service_dependencies "$target_service") || {
+            err "Failed to get dependencies for $DARKYELLOW$target_service$NORMAL"
+            return 1
+        }
         debug "  $DARKYELLOW$target_service$NORMAL deps:$DARKYELLOW" $services "$NORMAL$GRAY(in $((SECONDS - start))s)$NORMAL"
         for service in $services; do
 
@@ -808,7 +814,10 @@ get_docker_compose () {
             ## mark the service as "loaded" as well as it's containers
             ## if this is a subordinate service
             start_service=$SECONDS
-            entries[$service]=$(_get_docker_compose_service_mixin "$service") || return 1
+            entries[$service]=$(_get_docker_compose_service_mixin "$service") || {
+                err "Failed to get service mixin for $DARKYELLOW$service$NORMAL"
+                return 1
+            }
             debug "    Applied $DARKYELLOW$service$NORMAL charm metadata mixins $GRAY(in $((SECONDS - start_service))s)$NORMAL"
         done
         debug "    ..finished all mixins for $DARKYELLOW$target_service$NORMAL $GRAY(in $((SECONDS - start))s)$NORMAL"