php artisan db:seed command not working

I am going to install Laratrust to My laravel project. when I am going to run following command

php artisan db:seed command not working

occurred following error in cmd

Class 'Laratrust\LaratrustRole' not found

My Role Model is this

<?php

namespace App;

use Laratrust\LaratrustRole;

class Role extends LaratrustRole
{
    //
}