diff --git a/mercurial/manifest.py b/mercurial/manifest.py
--- a/mercurial/manifest.py
+++ b/mercurial/manifest.py
@@ -44,7 +44,7 @@ class manifest(revlog):
         if self.listcache and self.addlist and self.listcache[0] == a:
             d = mdiff.diff(self.listcache[1], self.addlist, 1)
             if mdiff.patch(a, d) != b:
-                raise AssertionError("sortdiff failed!")
+                raise AssertionError(_("sortdiff failed!"))
             return d
         else:
             return mdiff.textdiff(a, b)
@@ -145,7 +145,7 @@ class manifest(revlog):
                     end = bs
                     if w[1] == 1:
                         raise AssertionError(
-                            "failed to remove %s from manifest\n" % f)
+                            _("failed to remove %s from manifest\n") % f)
                 else:
                     # item is found, replace/delete the existing line
                     end = bs + 1
@@ -159,7 +159,7 @@ class manifest(revlog):
 
         text = "".join(self.addlist)
         if cachedelta and mdiff.patch(self.listcache[0], cachedelta) != text:
-            raise AssertionError("manifest delta failure\n")
+            raise AssertionError(_("manifest delta failure\n"))
         n = self.addrevision(text, transaction, link, p1, p2, cachedelta)
         self.mapcache = (n, map, flags)
         self.listcache = (text, self.addlist)