Unlock defaultArnoldRenderOptions attributes

Greetings,

I have to create a skyShader and connect it with the defaultArnoldRenderOptions.background node. I am unable to do it successfully and get the following error.

Command
mc.setAttr( "defaultArnoldRenderOptions.background", lock=False)
mc.setAttr("defaultArnoldRenderOptions.background", "aiSkyTransform",type="string")

Error
# Error: setAttr: The attribute 'defaultArnoldRenderOptions.background' is locked or connected and cannot be modified.
# Traceback (most recent call last):
#   File "<maya console>", line 1, in <module>
# RuntimeError: setAttr: The attribute 'defaultArnoldRenderOptions.background' is locked or connected and cannot be modified. #

Please suggest me  a way to get this working.

Thanks

You would need to use connectAttr, and hook up the message attribute of the aiSky node (not a transform):

Thanks spire2