diff -r c093cc6e6c99 -r 313e3a279828 mercurial/changegroup.py
--- a/mercurial/changegroup.py	Thu Nov 07 03:59:22 2019 -0800
+++ b/mercurial/changegroup.py	Thu Nov 07 13:18:19 2019 -0500
@@ -85,7 +85,7 @@
                 fh = open(filename, b"wb", 131072)
         else:
             fd, filename = pycompat.mkstemp(prefix=b"hg-bundle-", suffix=b".hg")
-            fh = os.fdopen(fd, r"wb")
+            fh = os.fdopen(fd, "wb")
         cleanup = filename
         for c in chunks:
             fh.write(c)