Fix HMAC initialization compatibility with Python 3.8 and newer.
Explicitly specify MD5 as the digest algorithm, since hmac.new()
no longer accepts an omitted digestmod argument. Preserve the
original HMAC-MD5 algorithm used for XSRF token generation.
--- ../oauth2client/contrib/xsrfutil.py	2026-10-16 17:34:35.127390105 +0300
+++ ../oauth2client/contrib/xsrfutil.py	2026-10-16 17:36:13.601131820 +0300
@@ -17,6 +17,7 @@
 import base64
 import binascii
 import hmac
+import hashlib
 import time
 
 from oauth2client import _helpers
@@ -44,7 +45,9 @@
     Returns:
         A string XSRF protection token.
     """
-    digester = hmac.new(_helpers._to_bytes(key, encoding='utf-8'))
+    digester = hmac.new(
+        _helpers._to_bytes(key, encoding='utf-8'),
+        digestmod=hashlib.md5)
     digester.update(_helpers._to_bytes(str(user_id), encoding='utf-8'))
     digester.update(DELIMITER)
     digester.update(_helpers._to_bytes(action_id, encoding='utf-8'))