src/Validators/UniqueValidator.php
public function init()
    {
        parent::init();
        if ($this->message !== null) {
            return;
        }
        if (is_array($this->targetAttribute) && count($this->targetAttribute) > 1) {
            $this->message = Reaction::t('rct', 'The combination {values} of {attributes} has already been taken.');
        } else {
            $this->message = Reaction::t('rct', '{attribute} "{value}" has already been taken.');
        }
    }
public function init()
    {
        parent::init();
        if ($this->message !== null) {
            return;
        }
        if (is_array($this->targetAttribute) && count($this->targetAttribute) > 1) {
            $this->message = Reaction::t('rct', 'The combination {values} of {attributes} has already been taken.');
        } else {
            $this->message = Reaction::t('rct', '{attribute} "{value}" has already been taken.');
        }
    }
{@inheritdoc}