diff -r 968b29a5a7fc -r 5aafc3c5bdec mercurial/pure/mpatch.py
--- a/mercurial/pure/mpatch.py	Sun Feb 20 14:52:40 2022 -0700
+++ b/mercurial/pure/mpatch.py	Sun Feb 20 15:03:26 2022 -0700
@@ -7,11 +7,11 @@
 
 from __future__ import absolute_import
 
+import io
 import struct
 
-from .. import pycompat
 
-stringio = pycompat.bytesio
+stringio = io.BytesIO
 
 
 class mpatchError(Exception):