code: private String getFailureReason(final FileUploadId fileUploadId) {
          String failureReason = "";
          if (artifactUploadState.getFileUploadProgress(fileUploadId) != null) {
              failureReason = artifactUploadState.getFileUploadProgress(fileUploadId).getFailureReason();
          }
          if (StringUtils.isEmpty(failureReason)) {
              return "";
          }
          return failureReason;
      }
docs: Returns the failure reason for the provided fileUploadId or an empty
  string but never <code>null</code>.
  
  @param fileUploadId
  @return the failure reason or an empty String.