diff -r e32dfff71529 -r fdd22bf6398f mercurial/repository.py
--- a/mercurial/repository.py	Sun Apr 01 22:48:32 2018 -0700
+++ b/mercurial/repository.py	Wed Apr 04 14:31:09 2018 -0700
@@ -446,7 +446,7 @@
     def lookup(key):
         """Resolve the node for a revision."""
 
-    def lookupbranch(key, remote=None):
+    def lookupbranch(key):
         """Look up the branch name of the given revision or branch name."""
 
     def known(nodes):