In method close() the ActorSystemProviderImpl waits 10 seconds for the ActorSystem to terminate.

try {
  Await.result(actorSystem.terminate(), FiniteDuration.create(10, TimeUnit.SECONDS));
} catch (final Exception e) {
  LOG.warn("Error awaiting actor termination", e);
}

If the timeout is reached TimeoutException is thrown. However it is immediately caught and only logged. The caller has no idea something went wrong. 
This exception should be propagated.