Answered How do I throw an error from within a processor?

class scStudentAssignmentUpdateProcessor extends modObjectUpdateProcessor {
    
    public $classKey = 'scStudentAssignment';
    public $languageTopics = array('studentcentre:default');
    public $objectType = 'studentcentre.ass';
    
	public function beforeSet() {
		$comment = $this->getProperty('comment');
		$saId = $this->getProperty('id');
		$userId = $this->getProperty('userId');
		$processorsPath = $this->getProperty('processorsPath');
		
		if (empty($comment)) { // check to see if the comment field is empty. if so throw error response
            $this->addFieldError('comment',$this->modx->lexicon('studentcentre.ass_err_ns_comment'));
        } else {
        	$response = $this->modx->runProcessor('mgr/assignments/scCommentCreate', array(
					'comment' => $comment,
					'student_assignment_id' => $saId,
					'user_id' => $userId,
				), array(
					'processors_path' => $processorsPath,
				)
			);
			
			if ($response->isError()) {
			    return $this->failure($response->getMessage());
			}
        }

		return parent::beforeSet();
	}
}

return 'scStudentAssignmentUpdateProcessor';