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/shelve.py

@@ -138,17 +138,21 @@ class Shelf(collections.MutableMapping):
         self.close()
 
     def close(self):
-        self.sync()
+        if self.dict is None:
+            return
         try:
-            self.dict.close()
-        except AttributeError:
-            pass
-        # Catch errors that may happen when close is called from __del__
-        # because CPython is in interpreter shutdown.
-        try:
-            self.dict = _ClosedDict()
-        except (NameError, TypeError):
-            self.dict = None
+            self.sync()
+            try:
+                self.dict.close()
+            except AttributeError:
+                pass
+        finally:
+            # Catch errors that may happen when close is called from __del__
+            # because CPython is in interpreter shutdown.
+            try:
+                self.dict = _ClosedDict()
+            except:
+                self.dict = None
 
     def __del__(self):
         if not hasattr(self, 'writeback'):