/**
  * Method used for errors processing
  *
  * @param error error caused by this request
  */
 private void provideError(final VKError error) {
   error.request = this;
   if (requestListener != null) {
     requestListener.onError(error);
   }
   if (mPostRequestsQueue != null && mPostRequestsQueue.size() > 0) {
     for (VKRequest postRequest : mPostRequestsQueue)
       if (postRequest.requestListener != null) postRequest.requestListener.onError(error);
   }
 }