Blender Version
Broken: 2.80
Short description of error
Right clicking the 'Strength' value of a cycles node-based lamp, and selecting 'copy data path' results in:
nodes["Emission"].inputs[1].default_value
This seems to be incorrect, as it cannot be pasted into a driver directly, rather it should be:
node_tree.nodes["Emission"].inputs[1].default_value