diff --git a/mercurial/simplemerge.py b/mercurial/simplemerge.py
--- a/mercurial/simplemerge.py
+++ b/mercurial/simplemerge.py
@@ -27,10 +27,6 @@
 from .utils import stringutil
 
 
-class CantReprocessAndShowBase(Exception):
-    pass
-
-
 def intersect(ra, rb):
     """Given two ranges return the range where they intersect or None.
 
diff --git a/tests/test-simplemerge.py b/tests/test-simplemerge.py
--- a/tests/test-simplemerge.py
+++ b/tests/test-simplemerge.py
@@ -48,9 +48,6 @@
         )
 
 
-CantReprocessAndShowBase = simplemerge.CantReprocessAndShowBase
-
-
 def split_lines(t):
     return util.stringio(t).readlines()