private String dumpProgressToken(ProgressToken token) {
        StringBuilder builder = new StringBuilder();
        builder.append("#total: ").append(token.getTotalBucketCount()).append('\n');
        builder.append("#finished: ").append(token.getFinishedBucketCount()).append('\n');
        if (token.containsFailedBuckets()) {
            builder.append("failed:\n");
            Map<BucketId, BucketId> failed = token.getFailedBuckets();
            for (Map.Entry<BucketId, BucketId> kv : failed.entrySet()) {
                builder.append(kv.getKey()).append(" : ").append(kv.getValue()).append('\n');
            }
        }
        return builder.toString();
    }
Test branch where we don't know how to handle a certain reply type.
This should never happen (since we only get replies for messages we've
already sent) but deal with it anyway!
documentapi/src/test/java/com/yahoo/documentapi/messagebus/MessageBusVisitorSessionTestCase.java