public function validateSlugUpdate( $attribute, $params ) {

		if( !$this->hasErrors() ) {

			$existingUser = self::findBySlug( $this->slug );

			if( isset( $existingUser ) && $this->id != $existingUser->id ) {

				$this->addError( $attribute, Yii::$app->coreMessage->getMessage( CoreGlobal::ERROR_SLUG_EXIST ) );
			}
		}
	}