Refs #32191 -- Removed for the pre-Django 3.2 format of messages in CookieStorage.

Per deprecation timeline.

django/contrib/messages/storage/cookie.py

@@ -161,21 +161,8 @@ class CookieStorage(BaseStorage):
             return None
         try:
             return self.signer.unsign_object(data, serializer=MessageSerializer)
-        # RemovedInDjango41Warning: when the deprecation ends, replace with:
-        #
-        # except (signing.BadSignature, json.JSONDecodeError):
-        #     pass
-        except signing.BadSignature:
-            decoded = None
-        except (binascii.Error, json.JSONDecodeError):
-            decoded = self.signer.unsign(data)
-
-        if decoded:
-            # RemovedInDjango41Warning.
-            try:
-                return json.loads(decoded, cls=MessageDecoder)
-            except json.JSONDecodeError:
-                pass
+        except (signing.BadSignature, binascii.Error, json.JSONDecodeError):
+            pass
         # Mark the data as used (so it gets removed) since something was wrong
         # with the data.
         self.used = True

docs/releases/4.1.txt

@@ -263,3 +263,6 @@ to remove usage of these features.
 
 * The ``django.core.cache.backends.memcached.MemcachedCache`` backend is
   removed.
+
+* Support for the pre-Django 3.2 format of messages used by
+  ``django.contrib.messages.storage.cookie.CookieStorage`` is removed.

tests/messages_tests/test_cookie.py

@@ -1,4 +1,3 @@
-import binascii
 import json
 import random
 
@@ -8,7 +7,6 @@ from django.contrib.messages.storage.base import Message
 from django.contrib.messages.storage.cookie import (
     CookieStorage, MessageDecoder, MessageEncoder,
 )
-from django.core.signing import b64_decode, get_cookie_signer
 from django.test import SimpleTestCase, override_settings
 from django.utils.crypto import get_random_string
 from django.utils.safestring import SafeData, mark_safe
@@ -179,18 +177,3 @@ class CookieTests(BaseTests, SimpleTestCase):
         storage = self.get_storage()
         self.assertIsInstance(encode_decode(mark_safe("<b>Hello Django!</b>")), SafeData)
         self.assertNotIsInstance(encode_decode("<b>Hello Django!</b>"), SafeData)
-
-    def test_legacy_encode_decode(self):
-        # RemovedInDjango41Warning: pre-Django 3.2 encoded messages will be
-        # invalid.
-        storage = self.storage_class(self.get_request())
-        messages = ['this', Message(0, 'Successfully signed in as admin@example.org')]
-        # Encode/decode a message using the pre-Django 3.2 format.
-        encoder = MessageEncoder()
-        value = encoder.encode(messages)
-        with self.assertRaises(binascii.Error):
-            b64_decode(value.encode())
-        signer = get_cookie_signer(salt=storage.key_salt)
-        encoded_messages = signer.sign(value)
-        decoded_messages = storage._decode(encoded_messages)
-        self.assertEqual(messages, decoded_messages)