framework/validators/RegularExpressionValidator.php
public function init()
    {
        parent::init();
        if ($this->pattern === null) {
            throw new InvalidConfigException('The "pattern" property must be set.');
        }
        if ($this->message === null) {
            $this->message = Yii::t('yii', '{attribute} is invalid.');
        }
    }
public function init()
    {
        parent::init();
        if ($this->pattern === null) {
            throw new InvalidConfigException('The "pattern" property must be set.');
        }
        if ($this->message === null) {
            $this->message = Yii::t('yii', '{attribute} is invalid.');
        }
    }
{@inheritdoc}