docs: def routeMessage(self, sender, target, value, messageID):
          """
          Implement L{IMessageRouter.routeMessage} by synchronously locating an
          account via L{axiom.userbase.LoginSystem.accountByAddress}, and
          delivering a message to it by calling a method on it.
          """
          router = self._routerForAccount(target)
          if router is not None:
              router.routeMessage(sender, target, value, messageID)
          else:
              reverseRouter = self._routerForAccount(sender)
              reverseRouter.routeAnswer(sender, target,
                                        Value(DELIVERY_ERROR, ERROR_NO_USER),
                                        messageID)