Issue #3303559 by aleix: Check if private directory is configured

activitypub.install

@@ -27,7 +27,7 @@ function activitypub_requirements($phase) {
       }
 
       if (!\Drupal::hasService('stream_wrapper.private') || !is_dir($path)) {
-        $description = t('An automated attempt to create the directory %directory failed, possibly due to a permissions problem. To proceed with the installation, either create the directory and modify its permissions manually or ensure that the installer has the permissions to create it automatically. For more information, see INSTALL.txt or the <a href=":handbook_url">online handbook</a>.', ['%directory' => $path, ':handbook_url' => 'https://www.drupal.org/server-permissions']);
+        $description = t('An automated attempt to create the directory %directory failed, possibly due to a permissions problem or issues with how private files are set. Documentation about private files can be found in <a href=":private_files_docs">drupal docs</a>. To proceed with the installation, either create the directory and modify its permissions manually or ensure that private files are working and that the installer has the permissions to create it automatically. For more information, see INSTALL.txt or the <a href=":handbook_url">online handbook</a>.', ['%directory' => $path, ':private_files_docs'=>'https://www.drupal.org/docs/8/core/modules/file/overview#s-managing-file-locations-and-access',  ':handbook_url' => 'https://www.drupal.org/server-permissions']);
         $requirements['activitypub_directory_' . $delta] = [
           'title' => $label,
           'description' => $description,