Issue #11915: threading.RLock()._release_save() raises a RuntimeError if the
lock was not acquired.
diff --git a/Lib/test/lock_tests.py b/Lib/test/lock_tests.py
index ff30d41..3ed61f3 100644
--- a/Lib/test/lock_tests.py
+++ b/Lib/test/lock_tests.py
@@ -247,6 +247,7 @@
         # Cannot release an unacquired lock
         lock = self.locktype()
         self.assertRaises(RuntimeError, lock.release)
+        self.assertRaises(RuntimeError, lock._release_save)
         lock.acquire()
         lock.acquire()
         lock.release()
@@ -254,6 +255,7 @@
         lock.release()
         lock.release()
         self.assertRaises(RuntimeError, lock.release)
+        self.assertRaises(RuntimeError, lock._release_save)
 
     def test_different_thread(self):
         # Cannot release from a different thread