diff -r 2806c7bbcb5e -r d7626e85dada mercurial/keepalive.py
--- a/mercurial/keepalive.py	Thu Jun 01 18:23:20 2017 -0700
+++ b/mercurial/keepalive.py	Fri Jun 02 14:08:26 2017 -0700
@@ -354,7 +354,8 @@
 
     def __init__(self, sock, debuglevel=0, strict=0, method=None):
         httplib.HTTPResponse.__init__(self, sock, debuglevel=debuglevel,
-                                      strict=True, method=method)
+                                      strict=True, method=method,
+                                      buffering=True)
         self.fileno = sock.fileno
         self.code = None
         self._rbuf = ''