diff -r 649d3ac37a12 -r d783f945a701 mercurial/url.py
--- a/mercurial/url.py	Sun Oct 06 19:25:18 2019 -0400
+++ b/mercurial/url.py	Mon Oct 07 00:04:04 2019 -0400
@@ -232,7 +232,7 @@
         ]
     )
     self.send(b'CONNECT %s HTTP/1.0\r\n' % self.realhostport)
-    for header in proxyheaders.iteritems():
+    for header in pycompat.iteritems(proxyheaders):
         self.send(b'%s: %s\r\n' % header)
     self.send(b'\r\n')