Issue #7282: Fix a memory leak when an RLock was used in a thread other

than those started through `threading.Thread` (for example, using
`thread.start_new_thread()`.

Lib/test/test_threading.py

@@ -143,11 +143,9 @@ class ThreadTests(BaseTestCase):
     def test_foreign_thread(self):
         # Check that a "foreign" thread can use the threading module.
         def f(mutex):
-            # Acquiring an RLock forces an entry for the foreign
+            # Calling current_thread() forces an entry for the foreign
             # thread to get made in the threading._active map.
-            r = threading.RLock()
-            r.acquire()
-            r.release()
+            threading.current_thread()
             mutex.release()
 
         mutex = threading.Lock()