Distinguish notice saving errors from others for Salmon

classes/Notice.php

@@ -950,7 +950,7 @@ class Notice extends Managed_DataObject
                 $object = null;
                 Event::handle('StoreActivityObject', array($act, $stored, $options, &$object));
                 if (empty($object)) {
-                    throw new ServerException('Unsuccessful call to StoreActivityObject '.$stored->getUri() . ': '.$act->asString());
+                    throw new NoticeSaveException('Unsuccessful call to StoreActivityObject '._ve($stored->getUri()) . ': '._ve($act->asString()));
                 }
 
                 // If something changed in the Notice during StoreActivityObject

lib/noticesaveexception.php

@@ -0,0 +1,17 @@
+<?php
+
+if (!defined('GNUSOCIAL')) { exit(1); }
+
+/**
+ * Base exception class for when a notice cannot be saved
+ *
+ * @category Exception
+ * @package  GNUsocial
+ * @author   Mikael Nordfeldth <mmn@hethane.se>
+ * @license  https://www.gnu.org/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link     https://gnu.io/social
+ */
+
+class NoticeSaveException extends ServerException
+{
+}

plugins/OStatus/lib/salmonaction.php

@@ -109,6 +109,8 @@ class SalmonAction extends Action
             // duplicate? Maybe someone's database is out of sync?
             // Let's just accept it and move on.
             common_log(LOG_INFO, 'Salmon slap carried an event which had already been fulfilled.');
+        } catch (NoticeSaveException $e) {
+            common_debug('Notice::saveActivity did not save our '._ve($this->activity->verb).' activity, trying old-fashioned salmon saving.');
         }
 
         try {