Fix refleak at test suite level

Author: corona10

Lib/importlib/_bootstrap.py

@@ -86,7 +86,6 @@ def __exit__(self, *args, **kwargs):
         """Remove self.lock from this thread's _blocking_on list."""
         self.blocked_on.remove(self.lock)
 
-
 class _DeadlockError(RuntimeError):
     pass
 

Lib/test/test_importlib/test_locks.py

@@ -33,6 +33,11 @@ class ModuleLockAsRLockTests:
     test_repr = None
     test_locked_repr = None
 
+    def tearDown(self):
+        for splitinit in init.values():
+            splitinit._bootstrap._blocking_on.clear()
+
+
 LOCK_TYPES = {kind: splitinit._bootstrap._ModuleLock
               for kind, splitinit in init.items()}