Set stacklevel for the override_settings warning.

Refs #19031.

django/test/signals.py

@@ -97,4 +97,7 @@ def file_storage_changed(**kwargs):
 @receiver(setting_changed)
 def complex_setting_changed(**kwargs):
     if kwargs['enter'] and kwargs['setting'] in COMPLEX_OVERRIDE_SETTINGS:
-        warnings.warn("Overriding setting %s can lead to unexpected behaviour." % kwargs['setting'])
+        # Considering the current implementation of the signals framework,
+        # stacklevel=5 shows the line containing the override_settings call.
+        warnings.warn("Overriding setting %s can lead to unexpected behaviour."
+                      % kwargs['setting'], stacklevel=5)

tests/settings_tests/tests.py

@@ -227,13 +227,13 @@ class TestComplexSettingOverride(TestCase):
         with warnings.catch_warnings(record=True) as w:
             warnings.simplefilter("always")
 
-            override = override_settings(TEST_WARN='override')
-            override.enable()
-            self.assertEqual('override', settings.TEST_WARN)
-            override.disable()
+            with override_settings(TEST_WARN='override'):
+                self.assertEqual(settings.TEST_WARN, 'override')
 
             self.assertEqual(len(w), 1)
-            self.assertEqual('Overriding setting TEST_WARN can lead to unexpected behaviour.', str(w[-1].message))
+            self.assertEqual(w[0].filename, __file__)
+            self.assertEqual(str(w[0].message),
+                'Overriding setting TEST_WARN can lead to unexpected behaviour.')
 
 
 class UniqueSettingsTests(TestCase):