[fix] debconf: use error instead of note (#1524)

When encountered, errors are always showed.

debian/alternc.config

@@ -248,10 +248,8 @@ while [ "$QUEST_STATE" != 0 -a "$QUEST_STATE" != 14 ]; do
     touch "$aclcheckfile"
     setfacl -m u:root:rwx "$aclcheckfile" 2>/dev/null || (
       test -e "$aclcheckfile" && rm -f "$aclcheckfile" || true
-      db_input critical alternc/acluninstalled || true
-      db_go
-      db_reset alternc/acluninstalled || true
-      db_fset alternc/acluninstalled "seen" "false" || true
+      db_input high alternc/acluninstalled || true
+      db_go || true
       exit 2
     )
     test -e "$aclcheckfile" && rm -f "$aclcheckfile" || true

debian/alternc.templates

@@ -1,11 +1,14 @@
 Template: alternc/acluninstalled
-Type: note
+Type: error
 _Description: AlternC need ACL on filesystem
  AlternC can't work without ACL activated on its filesystem.
  ACL are currently not enabled.
  .
  Also, you need to activate group quota (grpquota)
  to be able to use disk quota (but that's not mandatory).
+ .
+ This is a fatal error and will cause the package installation
+ to fail.
 
 Template: alternc/quotauninstalled
 Type: note