code: public String encode(String fileUrl) {
          String file = getFilePathFromWikiUrl(fileUrl);
          try {
              byte[] content = IOUtils.toByteArray(new FileInputStream(file));
              return base64Encode(content);
          } catch (IOException e) {
              throw new SlimFixtureException("Unable to read: " + file, e);
          }
      }
docs: Gets the content of specified file base64 encoded.
  @param fileUrl either absolute path, or link to file inside wiki's files section.
  @return base64 encoded file content.