Fixed #27688 -- Made messages' add_message() request check use ducktyping.

1 files changed, 15 insertions, 11 deletions

diff --git a/django/contrib/messages/api.py b/django/contrib/messages/api.py
index ceb6057f8d..f77cf26de5 100644
--- a/django/contrib/messages/api.py
+++ b/django/contrib/messages/api.py
@@ -1,6 +1,5 @@
 from django.contrib.messages import constants
 from django.contrib.messages.storage import default_storage
-from django.http import HttpRequest
 
 __all__ = (
     'add_message', 'get_messages',
@@ -18,16 +17,21 @@ def add_message(request, level, message, extra_tags='', fail_silently=False):
     """
     Attempts to add a message to the request using the 'messages' app.
     """
-    if not isinstance(request, HttpRequest):
-        raise TypeError("add_message() argument must be an HttpRequest object, "
-                        "not '%s'." % request.__class__.__name__)
-    if hasattr(request, '_messages'):
-        return request._messages.add(level, message, extra_tags)
-    if not fail_silently:
-        raise MessageFailure(
-            'You cannot add messages without installing '
-            'django.contrib.messages.middleware.MessageMiddleware'
-        )
+    try:
+        messages = request._messages
+    except AttributeError:
+        if not hasattr(request, 'META'):
+            raise TypeError(
+                "add_message() argument must be an HttpRequest object, not "
+                "'%s'." % request.__class__.__name__
+            )
+        if not fail_silently:
+            raise MessageFailure(
+                'You cannot add messages without installing '
+                'django.contrib.messages.middleware.MessageMiddleware'
+            )
+    else:
+        return messages.add(level, message, extra_tags)
 
 
 def get_messages(request):