bw compat import

schema.py

@@ -3,8 +3,11 @@
 :copyright: 2003-2009 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
 :contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
 """
-from yams.buildobjs import EntityType, RelationType, SubjectRelation, RichString
-
+from yams.buildobjs import EntityType, RelationType, SubjectRelation
+try:
+    from yams.buildobjs import RichString
+except:
+    from cubicweb.schema import RichString
 from cubicweb.schema import RRQLExpression
 
 class Comment(EntityType):