diff -r 7226f2626fb1 -r d748fd2647f8 mercurial/pure/mpatch.py
--- a/mercurial/pure/mpatch.py	Mon Jul 29 12:10:08 2024 -0400
+++ b/mercurial/pure/mpatch.py	Thu Jul 25 14:40:38 2024 -0400
@@ -106,7 +106,7 @@
             try:
                 p1, p2, l = struct.unpack(b">lll", m.read(12))
             except struct.error:
-                raise mpatchError(b"patch cannot be decoded")
+                raise mpatchError("patch cannot be decoded")
             _pull(new, frags, p1 - last)  # what didn't change
             _pull([], frags, p2 - p1)  # what got deleted
             new.append((l, pos + 12))  # what got added
@@ -137,7 +137,7 @@
         outlen += length
 
     if bin != binend:
-        raise mpatchError(b"patch cannot be decoded")
+        raise mpatchError("patch cannot be decoded")
 
     outlen += orig - last
     return outlen