diff -r c093cc6e6c99 -r 313e3a279828 mercurial/httppeer.py
--- a/mercurial/httppeer.py	Thu Nov 07 03:59:22 2019 -0800
+++ b/mercurial/httppeer.py	Thu Nov 07 13:18:19 2019 -0500
@@ -543,7 +543,7 @@
         try:
             # dump bundle to disk
             fd, filename = pycompat.mkstemp(prefix=b"hg-bundle-", suffix=b".hg")
-            with os.fdopen(fd, r"wb") as fh:
+            with os.fdopen(fd, "wb") as fh:
                 d = fp.read(4096)
                 while d:
                     fh.write(d)