Uncaught Error: No module: Panel

Uncaught Error: No module: Panel

I have seen that there are several similar questions (like this one) but
that answers not work for me.
app.coffee
"use strict"
angular.module('panel')
.config ['$routeProvider', '$locationProvider'], ($routeProvider,
$locationProvider) ->
$locationProvider.html5Mode true
$routeProvider
.when '/', {controller: Widgets, templateUrl: 'widgets.html'}
.otherwise {redirectTo: '/'}
return
Widgets = ($scope) ->
console.log 'Widgets init'
return
template.twig