[PATCH 1 of 2] py3: fix for Python 3.12 emitting SyntaxWarning on invalid escape sequences

[Mads Kiilerich]

# HG changeset patch
# User Mads Kiilerich <mads at kiilerich.com>
# Date 1679414842 -3600
#      Tue Mar 21 17:07:22 2023 +0100
# Branch stable
# Node ID 812482250f8d49159bb3024f08e0db38d0bad565
# Parent  87f0155d68aa56dcba2326692fff893c283cca96
py3: fix for Python 3.12 emitting SyntaxWarning on invalid escape sequences

Missed in 805d4a462abb:

  $ python3.12 mercurial/store.py
  mercurial/store.py:406: SyntaxWarning: invalid escape sequence '\.'
    EXCLUDED = re.compile(b'.*undo\.[^/]+\.(nd?|i)$')

diff --git a/mercurial/store.py b/mercurial/store.py
--- a/mercurial/store.py
+++ b/mercurial/store.py
@@ -403,7 +403,7 @@ REVLOG_FILES_VOLATILE_EXT = (b'.n', b'.n
 # some exception to the above matching
 #
 # XXX This is currently not in use because of issue6542
-EXCLUDED = re.compile(b'.*undo\.[^/]+\.(nd?|i)$')
+EXCLUDED = re.compile(br'.*undo\.[^/]+\.(nd?|i)$')
 
 
 def is_revlog(f, kind, st):