Add __getattr__(), __setattr__(), __delattr__() to 2.7 threading.local().

stdlib/2.7/threading.pyi

@@ -46,7 +46,9 @@ class ThreadError(Exception):
 
 class local(object):
     # TODO: allows arbitrary parameters...
-    pass
+    def __getattr__(self, name: str) -> Any: ...
+    def __setattr__(self, name: str, value: Any) -> None: ...
+    def __delattr__(self, name: str) -> None: ...
 
 class Event(object):
     def is_set(self) -> bool: ...