diff -r a2f139d25845 -r 70a7478c33de mercurial/subrepo.py
--- a/mercurial/subrepo.py	Sat Dec 13 14:53:46 2014 -0500
+++ b/mercurial/subrepo.py	Sat Dec 13 14:26:38 2014 -0500
@@ -442,7 +442,7 @@
         self.ui.warn("%s: %s" % (prefix, _("addremove is not supported")))
         return 1
 
-    def cat(self, ui, match, prefix, **opts):
+    def cat(self, match, prefix, **opts):
         return 1
 
     def status(self, rev2, **opts):
@@ -636,10 +636,10 @@
                                  dry_run, similarity)
 
     @annotatesubrepoerror
-    def cat(self, ui, match, prefix, **opts):
+    def cat(self, match, prefix, **opts):
         rev = self._state[1]
         ctx = self._repo[rev]
-        return cmdutil.cat(ui, self._repo, ctx, match, prefix, **opts)
+        return cmdutil.cat(self.ui, self._repo, ctx, match, prefix, **opts)
 
     @annotatesubrepoerror
     def status(self, rev2, **opts):