diff -r 28a450e1f54c -r 12998fd17fbc mercurial/verify.py
--- a/mercurial/verify.py	Mon Aug 02 13:30:03 2010 -0500
+++ b/mercurial/verify.py	Thu Aug 05 16:17:17 2010 -0500
@@ -48,6 +48,8 @@
         if isinstance(inst, KeyboardInterrupt):
             ui.warn(_("interrupted"))
             raise
+        if not str(inst):
+            inst = repr(inst)
         err(linkrev, "%s: %s" % (msg, inst), filename)
 
     def warn(msg):