code: def sign_certificate():
      
      LOGGER.info("Signing certificate...")
      cmd = [
          'openssl', 'req',
          '-in', os.path.join(gettempdir(), 'domain.csr'),
          '-outform', 'DER'
      ]
      devnull = open(os.devnull, 'wb')
      csr_der = subprocess.check_output(cmd, stderr=devnull)
      code, result = _send_signed_request(DEFAULT_CA + "/acme/new-cert", {
          "resource": "new-cert",
          "csr": _b64(csr_der),
      })
      if code != 201:
          raise ValueError("Error signing certificate: {0} {1}".format(code, result))
      LOGGER.info("Certificate signed!")
  
      return result
docs: Get the new certificate.
      Returns the signed bytes.