Issue #23207: merged fix from 3.4.

Lib/logging/__init__.py

@@ -1734,8 +1734,8 @@ def basicConfig(**kwargs):
                                      "specified together with 'handlers'")
             if handlers is None:
                 filename = kwargs.pop("filename", None)
+                mode = kwargs.pop("filemode", 'a')
                 if filename:
-                    mode = kwargs.pop("filemode", 'a')
                     h = FileHandler(filename, mode)
                 else:
                     stream = kwargs.pop("stream", None)

Lib/test/test_logging.py

@@ -3607,6 +3607,10 @@ class BasicConfigTest(unittest.TestCase):
                                                      handlers=handlers)
         assertRaises(ValueError, logging.basicConfig, stream=stream,
                                                      handlers=handlers)
+        # Issue 23207: test for invalid kwargs
+        assertRaises(ValueError, logging.basicConfig, loglevel=logging.INFO)
+        # Should pop both filename and filemode even if filename is None
+        logging.basicConfig(filename=None, filemode='a')
 
     def test_handlers(self):
         handlers = [