wecr_restricted_content_message_logged_in_create_topics.php

<?php
/**
 * Allows you to filter the stock bbPress message that reads 'You must be logged in to create new topics.'
 * 
 * @param string  $message      stock Easy Content Restriction message
 * @return string               Your custom message
 */
function  change_logged_in_topic_message( $message ) {
  return 'Our custom message';
} 
add_filter( 'wecr_restricted_content_message_logged_in_create_topics', 'change_logged_in_topic_message' );