local: raise AttributeError if '__dict__' attribute is set or deleted

--HG--
extra : transplant_source : %EA%99%1F%0F%C0Gq%98b%A7%0D%95%ABo%14%CF%18k%20f

gevent/local.py

@@ -185,6 +185,8 @@ class local(_localbase):
             return object.__getattribute__(self, name)
 
     def __setattr__(self, name, value):
+        if name == '__dict__':
+            raise AttributeError("%r object attribute '__dict__' is read-only" % self.__class__.__name__)
         d = object.__getattribute__(self, '_local__dicts').get(getcurrent())
         if d is None:
             lock = object.__getattribute__(self, '_local__lock')
@@ -199,6 +201,8 @@ class local(_localbase):
             return object.__setattr__(self, name, value)
 
     def __delattr__(self, name):
+        if name == '__dict__':
+            raise AttributeError("%r object attribute '__dict__' is read-only" % self.__class__.__name__)
         d = object.__getattribute__(self, '_local__dicts').get(getcurrent())
         if d is None:
             lock = object.__getattribute__(self, '_local__lock')