diff -r 4979ef2c0900 -r f728edc7fcd1 hgext/evolve.py
--- a/hgext/evolve.py	Fri Nov 15 19:14:19 2013 -0500
+++ b/hgext/evolve.py	Wed Jul 31 19:56:28 2013 +0200
@@ -1195,7 +1195,8 @@
         newer = [n for n in newer if n and ctx.node() not in n]
         if newer:
             return base, tuple(ctx._repo[o] for o in newer[0])
-    raise KeyError('Base seem unknown. This case is not handled yet.')
+    raise util.Abort('base of divergent changeset not found',
+                     hint='this case is not yet handled')