code: private static void log(final RqFallback req) throws IOException {
          final ByteArrayOutputStream baos = new ByteArrayOutputStream();
          final Throwable error = req.throwable();
          try (PrintStream stream = new Utf8PrintStream(baos, false)) {
              error.printStackTrace(stream);
          }
          FbSlf4j.LOGGER.error(
              "{} {} failed with {}: {}",
              new RqMethod.Base(req).method(),
              new RqHref.Base(req).href(),
              req.code(),
              baos.toString("UTF-8")
          );
      }
docs: Log this request.
  @param req Request
  @throws IOException If fails