diff -r bd2df58366b1 -r 65e2b64670b5 mercurial/error.py
--- a/mercurial/error.py	Tue Oct 06 20:37:35 2020 -0700
+++ b/mercurial/error.py	Tue Oct 06 20:45:52 2020 -0700
@@ -117,6 +117,11 @@
 class AmbiguousCommand(Exception):
     """Exception raised if command shortcut matches more than one command."""
 
+    def __init__(self, prefix, matches):
+        self.prefix = prefix
+        self.matches = matches
+        super(AmbiguousCommand, self).__init__()
+
     __bytes__ = _tobytes