RequireJS: finding the script responsible for an error

Question

I'm looking for an elegant way to find out the full path to a script that caused a timeout error (i.e. failed to load a dependency).

requirejs.onError = function (err) {

   // this works:
   var script_that_failed_loading = err.originalError.target.src

   // now I want:
   var the_script_responsible_for_this = <???>

};