Well, of course you'd want to make sure that the short is not located in any of the light fixtures first (the more likely case in my opinion). If not,
you would isolate each segment of the daisy chain and test it for shorting. At least then you'd know approximately where to start pulling off drywall.
If the drywaller put a screw or nail in the wire, then it's the electrician's fault for inadequately protecting the wires.