add comment to __getattr__ in RawProxy to clarify the intent of check

Author: dgpv

bitcoin/rpc.py

@@ -289,7 +289,10 @@ def __init__(self,
 
     def __getattr__(self, name):
         if name.startswith('__') and name.endswith('__'):
-            # Python internal stuff
+            # Prevent RPC calls for non-existing python internal attribute
+            # access. If someone tries to get an internal attribute
+            # of RawProxy instance, and the instance does not have this
+            # attribute, we do not want the bogus RPC call to happen.
             raise AttributeError
 
         # Create a callable to do the actual call