Issue #23016: A warning no longer produces an AttributeError when sys.stderr
is None.
diff --git a/Lib/test/test_warnings.py b/Lib/test/test_warnings.py
index fb2046e..7a9459a 100644
--- a/Lib/test/test_warnings.py
+++ b/Lib/test/test_warnings.py
@@ -560,6 +560,15 @@
         finally:
             globals_dict['__file__'] = oldfile
 
+    def test_stderr_none(self):
+        rc, stdout, stderr = assert_python_ok("-c",
+            "import sys; sys.stderr = None; "
+            "import warnings; warnings.simplefilter('always'); "
+            "warnings.warn('Warning!')")
+        self.assertEqual(stdout, b'')
+        self.assertNotIn(b'Warning!', stderr)
+        self.assertNotIn(b'Error', stderr)
+
 
 class WarningsDisplayTests(unittest.TestCase):