test_packaging should clean up after itself (but it doesn't really)

Lib/packaging/tests/__main__.py

@@ -5,15 +5,18 @@
 import os
 import sys
 import unittest
-from test.support import run_unittest, reap_children
+from test.support import run_unittest, reap_children, reap_threads
 
 
+@reap_threads
 def test_main():
-    start_dir = os.path.dirname(__file__)
-    top_dir = os.path.dirname(os.path.dirname(start_dir))
-    test_loader = unittest.TestLoader()
-    run_unittest(test_loader.discover(start_dir, top_level_dir=top_dir))
-    reap_children()
+    try:
+        start_dir = os.path.dirname(__file__)
+        top_dir = os.path.dirname(os.path.dirname(start_dir))
+        test_loader = unittest.TestLoader()
+        run_unittest(test_loader.discover(start_dir, top_level_dir=top_dir))
+    finally:
+        reap_children()
 
 
 if __name__ == '__main__':