framework/validators/UrlValidator.php
public function init()
    {
        parent::init();
        if ($this->enableIDN && !function_exists('idn_to_ascii')) {
            throw new InvalidConfigException('In order to use IDN validation intl extension must be installed and enabled.');
        }
        if ($this->message === null) {
            $this->message = Yii::t('yii', '{attribute} is not a valid URL.');
        }
    }
public function init()
    {
        parent::init();
        if ($this->enableIDN && !function_exists('idn_to_ascii')) {
            throw new InvalidConfigException('In order to use IDN validation intl extension must be installed and enabled.');
        }
        if ($this->message === null) {
            $this->message = Yii::t('yii', '{attribute} is not a valid URL.');
        }
    }
{@inheritdoc}