/**
  * Try to find the consumer for the provided request's consumer key.
  *
  * @param JacobKiers\OAuth\Request\RequestInterface $request
  *
  * @return JacobKiers\OAuth\Consumer\ConsumerInterface
  *
  * @throws JacobKiers\OAuth\OAuthException
  */
 private function getConsumer(RequestInterface $request)
 {
     $consumer_key = $request instanceof RequestInterface ? $request->getOAuthConsumerKey() : null;
     if (!$consumer_key) {
         throw new OAuthException('Invalid consumer key');
     }
     $consumer = $this->data_store->lookupConsumer($consumer_key);
     if (!$consumer) {
         throw new OAuthException('Invalid consumer');
     }
     return $consumer;
 }