Add note about instantiation to config.Config.from_object

flask/config.py

@@ -156,6 +156,14 @@ class Config(dict):
             from yourapplication import default_config
             app.config.from_object(default_config)
 
+        Note that the object is *not* called / instantiated. If you need to
+        use an attribute of the object instance, such as an @property,
+        then instantiate the object manually before sending to this function::
+
+            my_obj = DefaultConfig()
+            app.config.from_object(my_obj)
+            app.config.from_object(DifferentConfig())
+
         You should not use this function to load the actual configuration but
         rather configuration defaults.  The actual config should be loaded
         with :meth:`from_pyfile` and ideally from a location not within the