fix: better user information if a needed package is not installed

src/rougail/config.py

@@ -403,7 +403,7 @@ suffix:
   disabled:
     variable: upgrade"""
     for process in processes:
-        if processes[process] or process == "output":
+        if processes[process]:
             objects = processes[process]
             rougail_process += """
   {NAME}:
@@ -443,14 +443,22 @@ suffix:
                     DEFAULT=objects[0]["name"]
                 )
         else:
+            if process == 'output':
+                prop = 'hidden'
+            else:
+                prop = 'disabled'
             rougail_process += """
   {NAME}:
     description: Select for {NAME}
-    hidden: true
     mandatory: false
+    {PROP}: true
     multi: true
+    default: ["You haven't installed \\\"{NAME}\\\" package for rougail"]
+    validators:
+      - jinja: Please install a rougail-{NAME}-* package.
 """.format(
                 NAME=normalize_family(process),
+                PROP=prop,
             )
     rougail_options += rougail_process
     convert = FakeRougailConvert(add_extra_options)