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);
          }
          Logger.getLogger(FbLog4j.class).error(
              String.format(
                  "%s %s failed with %s: %s",
                  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