Log changes failing reindex because of missing ref

Change-Id: Id89d84e3c0e577a244d6941d9929f4b840a4adb9
diff --git a/gerrit-pgm/src/main/java/com/google/gerrit/pgm/Reindex.java b/gerrit-pgm/src/main/java/com/google/gerrit/pgm/Reindex.java
index 0062c20..438d4b1 100644
--- a/gerrit-pgm/src/main/java/com/google/gerrit/pgm/Reindex.java
+++ b/gerrit-pgm/src/main/java/com/google/gerrit/pgm/Reindex.java
@@ -335,9 +335,13 @@
       try {
         Map<String, Ref> refs = repo.getAllRefs();
         for (Change c : db.changes().byProject(project)) {
-          Ref r = refs.get(c.currentPatchSetId().toRefName());
+          String refName = c.currentPatchSetId().toRefName();
+          Ref r = refs.get(refName);
           if (r != null) {
             byId.put(r.getObjectId(), new ChangeData(c));
+          } else {
+            fail("Failed to index change " + c.getId()
+                + " (" + refName + " not found)", true, null);
           }
         }
         walk();