[5.1.x] Refs #35326 -- Adjusted deprecation warning stacklevel in FileSystemStorage.OS_OPEN_FLAGS.

Backport of 47f18a7 from main.

Author: charettes

django/core/files/storage/filesystem.py

@@ -48,6 +48,7 @@ def __init__(
                 "Overriding OS_OPEN_FLAGS is deprecated. Use "
                 "the allow_overwrite parameter instead.",
                 RemovedInDjango60Warning,
+                stacklevel=2,
             )
 
     @cached_property

docs/releases/5.1.1.txt

@@ -23,3 +23,7 @@ Bugfixes
 * Adjusted the deprecation warning ``stacklevel`` in :meth:`.Model.save` and
   :meth:`.Model.asave` to correctly point to the offending call site
   (:ticket:`35060`).
+
+* Adjusted the deprecation warning ``stacklevel`` when using ``OS_OPEN_FLAGS``
+  in :class:`~django.core.files.storage.FileSystemStorage` to correctly point
+  to the offending call site (:ticket:`35326`).

tests/file_storage/tests.py

@@ -635,10 +635,11 @@ def setUp(self):
     def test_os_open_flags_deprecation_warning(self):
         msg = "Overriding OS_OPEN_FLAGS is deprecated. Use the allow_overwrite "
         msg += "parameter instead."
-        with self.assertWarnsMessage(RemovedInDjango60Warning, msg):
+        with self.assertWarnsMessage(RemovedInDjango60Warning, msg) as ctx:
             self.storage = self.storage_class(
                 location=self.temp_dir, base_url="/test_media_url/"
             )
+        self.assertEqual(ctx.filename, __file__)
 
 
 # RemovedInDjango60Warning: Remove this test class.