Fixed excluding of non-existent groups

src/mio/installer.py

@@ -37,9 +37,13 @@ class Installer:
         self.symlink = {}
         
     def add_group(self, name, exclude=[], chain=[]):
+        group = group_node(name, None, self)
+        if group in exclude:
+            mio.log.log(CHATTY, "excluding group '%s'" % group.name)
+            return None
         g = self.repository.get(name)
         if g == None:
-            return
+            return None
         exclude = exclusion_closure(exclude, g._parent)
         exclude = exclusion_closure(exclude, g)
         group = group_node(g.name[0], g, self)