[5.0.x] Fixed #34923 -- Avoided initializing LEVEL_TAGS when importing django.contrib.messages.

Regression in b7fe36ad37fb18c4bc7932c0aec6ae4f299b9622.

Thanks James Gillard for the report.

Backport of 311718feb5f1fb9ff794bbac0cda48cfc3410de8 from main

2 files changed, 4 insertions, 2 deletions

diff --git a/django/contrib/messages/apps.py b/django/contrib/messages/apps.py
index 09a9554b70..5bda152ab3 100644
--- a/django/contrib/messages/apps.py
+++ b/django/contrib/messages/apps.py
@@ -2,12 +2,13 @@ from django.apps import AppConfig
 from django.contrib.messages.storage import base
 from django.contrib.messages.utils import get_level_tags
 from django.core.signals import setting_changed
+from django.utils.functional import SimpleLazyObject
 from django.utils.translation import gettext_lazy as _
 
 
 def update_level_tags(setting, **kwargs):
     if setting == "MESSAGE_TAGS":
-        base.LEVEL_TAGS = get_level_tags()
+        base.LEVEL_TAGS = SimpleLazyObject(get_level_tags)
 
 
 class MessagesConfig(AppConfig):
diff --git a/django/contrib/messages/storage/base.py b/django/contrib/messages/storage/base.py
index 124049a5e2..5d89acfe69 100644
--- a/django/contrib/messages/storage/base.py
+++ b/django/contrib/messages/storage/base.py
@@ -1,7 +1,8 @@
 from django.conf import settings
 from django.contrib.messages import constants, utils
+from django.utils.functional import SimpleLazyObject
 
-LEVEL_TAGS = utils.get_level_tags()
+LEVEL_TAGS = SimpleLazyObject(utils.get_level_tags)
 
 
 class Message: