Log failure to access reviewer list for notification emails

If we fail to retrieve the PatchSetApprovals for a change to decide
on the cc list for a notification, log the error.

Hopefully this will make it easier to track down occasional
notification email delivery failures.

Change-Id: Ib6a7baf89b97e0bb93af4c3db9bcee39e61f7ef2

gerrit-server/src/main/java/com/google/gerrit/server/mail/ChangeEmail.java

@@ -329,6 +329,11 @@ public abstract class ChangeEmail extends NotificationEmail {
         add(RecipientType.CC, ap.getAccountId());
       }
     } catch (OrmException err) {
+      if (includeZero) {
+        log.warn("Cannot CC users that commented on updated change", err);
+      } else {
+        log.warn("Cannot CC users that reviewed updated change", err);
+      }
     }
   }