mercurial/exchange.py

--- a/mercurial/exchange.py	Fri Apr 13 11:37:37 2018 -0700
+++ b/mercurial/exchange.py	Fri Apr 13 12:13:42 2018 -0700
@@ -2170,7 +2170,8 @@
     if not remote.capable('clonebundles'):
         return
 
-    res = remote._call('clonebundles')
+    with remote.commandexecutor() as e:
+        res = e.callcommand('clonebundles', {}).result()
 
     # If we call the wire protocol command, that's good enough to record the
     # attempt.