title: Yii2: Cannot perform RBAC migration (You should configure "authManager"...)
body: <p>As it is described <a href="http://www.yiiframework.com/doc-2.0/yii-rbac-dbmanager.html">here</a> I'm trying to do the migration in order to let yii create the user authentication tables. However I get the error:</p>
  
  <blockquote>
    <p>Exception 'yii\base\InvalidConfigException' with message 'You should
    configure "authManager" component to use database before executing
    this migration.'</p>
  </blockquote>
  
  <p>The authManager is present in the configuration but I still get that error. Configuration:</p>
  
  <pre><code>'components' =&gt; [
      ...
      'db' =&gt; $db,
      'authManager'  =&gt; [
          'class'        =&gt; 'yii\rbac\DbManager',
          //            'defaultRoles' =&gt; ['guest'],
      ],
      ...
  ],
  </code></pre>
  
  <p>What's the problem?</p>