Index: lib/yaml/representer.py
===================================================================
--- lib/yaml/representer.py	(revision 385)
+++ lib/yaml/representer.py	(working copy)
@@ -244,7 +244,8 @@
         return self.represent_mapping(tag, state, flow_style=flow_style)
 
     def represent_undefined(self, data):
-        raise RepresenterError("cannot represent an object: %s" % data)
+        raise RepresenterError("cannot represent object %r of %r"
+                               % (data, type(data)))
 
 SafeRepresenter.add_representer(type(None),
         SafeRepresenter.represent_none)
@@ -409,7 +410,8 @@
         elif hasattr(data, '__reduce__'):
             reduce = data.__reduce__()
         else:
-            raise RepresenterError("cannot represent object: %r" % data)
+            raise RepresenterError("cannot represent object %r of %r"
+                                   % (data, type(data)))
         reduce = (list(reduce)+[None]*5)[:5]
         function, args, state, listitems, dictitems = reduce
         args = list(args)
Index: lib3/yaml/representer.py
===================================================================
--- lib3/yaml/representer.py	(revision 385)
+++ lib3/yaml/representer.py	(working copy)
@@ -224,7 +224,8 @@
         return self.represent_mapping(tag, state, flow_style=flow_style)
 
     def represent_undefined(self, data):
-        raise RepresenterError("cannot represent an object: %s" % data)
+        raise RepresenterError("cannot represent object %r of %r"
+                               % (data, type(data)))
 
 SafeRepresenter.add_representer(type(None),
         SafeRepresenter.represent_none)
@@ -314,7 +315,8 @@
         elif hasattr(data, '__reduce__'):
             reduce = data.__reduce__()
         else:
-            raise RepresenterError("cannot represent object: %r" % data)
+            raise RepresenterError("cannot represent object %r of %r"
+                                   % (data, type(data)))
         reduce = (list(reduce)+[None]*5)[:5]
         function, args, state, listitems, dictitems = reduce
         args = list(args)