Diagnose "node spawn ENOENT"

spawn-enoent.js

(function() {
    var childProcess = require("child_process");
    var oldSpawn = childProcess.spawn;
    function mySpawn() {
        console.log('spawn called');
        console.log(arguments);
        return oldSpawn.apply(this, arguments);
    }
    childProcess.spawn = mySpawn;
})();

found at http://stackoverflow.com/questions/27688804/how-do-i-debug-error-spawn-enoent-on-node-js