@Override
    public void onException(final Exception e) {
        this.exception = e;
        MAIN_THREAD_HANDLER.obtainMessage(MSG_EXCEPTION, this).sendToTarget();
    }
A class that manages a load by adding and removing callbacks for for the load and notifying callbacks when the
load completes.
core/src/main/java/com/bumptech/glide/load/engine/EngineJob.java