When running this function requesting "voxel-hello-world" I'm getting a strange error: ReferenceError: Can't find variable: voxel This is both strange because

gistfile1.txt

function fetchBundle(bundleName, preferredVersions, cb){

    var er = sandbox.bundle(bundleName, null)

    sandbox.on('bundleEnd', function(html){
      
	//Just to test, this IS returning bundle HTML, so I seem to be calling sandbox.bundle() correctly.

    })

    sandbox.on('modules', function(packages){
      
	//This event is never being thrown.

    })

    if(er){
      console.log("Sandbox error: "+er)  //This error never gets returned.
    }

}