public function passwordRequirements($attribute)
    {
        if (!preg_match('~\p{Lu}~', $this->$attribute) ||
            !preg_match('~\p{Ll}~', $this->$attribute) ||
            !preg_match('~[0-9]~', $this->$attribute) ||
            mb_strlen($this->$attribute, 'UTF-8') < 6 ||
            mb_strlen($this->$attribute, 'UTF-8') > 100) {
            $this->addError($attribute, Yii::t('podium/view', 'Password must contain uppercase and lowercase letter, digit, and be at least 6 characters long.'));
        }
    }