[__sensible_editor] List available editors when an incorrect one is provided

cdist/conf/type/__sensible_editor/explorer/editor_path

@@ -28,7 +28,10 @@ die() {
 }
 
 editor_missing() { die "Editor '$1' is missing on the target system."; }
-editor_no_alternative() { die "Editor '$1' is not in the alternatives list of the target system."; }
+editor_no_alternative() {
+	die "Editor '$1' is not in the alternatives list of the target system." \
+		"$(test "${editors}" && echo "\nPlease choose one of:\n\n${editors}")"
+}
 
 
 case $("${__explorer}/os")
@@ -63,7 +66,7 @@ in
 esac
 
 
-if $has_alternatives && test "$(echo "${editors}" | wc -l)" -gt 0
+if $has_alternatives && test -n "${editors}"
 then
 	IFS='
 '