Improve non-existent custom link message

src/Batch/BatchUrlGenerator.php

@@ -24,7 +24,7 @@ class BatchUrlGenerator {
   use StringTranslationTrait;
 
   const ANONYMOUS_USER_ID = 0;
-  const PATH_DOES_NOT_EXIST_OR_NO_ACCESS_MESSAGE = "The path @path has been omitted from the XML sitemap as it either does not exist, or it is not accessible to anonymous users.";
+  const PATH_DOES_NOT_EXIST_OR_NO_ACCESS_MESSAGE = "The custom path @path has been omitted from the XML sitemap as it either does not exist, or it is not accessible to anonymous users. You can review custom paths <a href='@custom_paths_url'>here</a>.";
   const PROCESSING_PATH_MESSAGE = 'Processing path #@current out of @max: @path';
   const REGENERATION_FINISHED_MESSAGE = "The <a href='@url' target='_blank'>XML sitemap</a> has been regenerated for all languages.";
   const REGENERATION_FINISHED_ERROR_MESSAGE = 'The sitemap generation finished with an error.';
@@ -169,7 +169,8 @@ class BatchUrlGenerator {
       // todo: Change to different function, as this also checks if current user has access. The user however varies depending if process was started from the web interface or via cron/drush. Use getUrlIfValidWithoutAccessCheck()?
       if (!$this->pathValidator->isValid($custom_path['path'])) {
 //        if (!(bool) $this->pathValidator->getUrlIfValidWithoutAccessCheck($custom_path['path'])) {
-        $this->logger->m(self::PATH_DOES_NOT_EXIST_OR_NO_ACCESS_MESSAGE, ['@path' => $custom_path['path']])
+        $this->logger->m(self::PATH_DOES_NOT_EXIST_OR_NO_ACCESS_MESSAGE,
+          ['@path' => $custom_path['path'], '@custom_paths_url' => $GLOBALS['base_url'] . '/admin/config/search/simplesitemap/custom'])
           ->display('warning', 'administer sitemap settings')
           ->log('warning');
         continue;