yii2: Proper way to throw new exception

Just for testing I have added this code in my model while setting the debug = true and false. ``` if($packagedays < 1) { throw new \yii\base\Exception( "package days cannot be less than 1" ); } ``` Now when Yii debug is true: I am getting Exception – yii\base\Exception package days cannot be less than 1 But when I am setting the debug to false I am getting Exception `An internal server error occurred.` The above error occurred while the Web server was processing your request. What I want is to replace the `An internal server error occurred.` with `package days cannot be less than 1` when `debug=false` What I am missing here? Thanks.