Issue #23865: close() methods in multiple modules now are idempotent and more

robust at shutdown. If needs to release multiple resources, they are released
even if errors are occured.

Lib/dbm/dumb.py

@@ -248,8 +248,10 @@ class _Database(collections.MutableMapping):
             raise error('DBM object has already been closed') from None
 
     def close(self):
-        self._commit()
-        self._index = self._datfile = self._dirfile = self._bakfile = None
+        try:
+            self._commit()
+        finally:
+            self._index = self._datfile = self._dirfile = self._bakfile = None
 
     __del__ = close