The error function now takes in a "RoutingError" structure. The idea is that the
structure includes all of the information necessary for a user to processor the
error as they wish. This interface is very incomplete and may change. At a
minimum, the error structure should include:
1) The request that failed.
2) Why the request failed.
3) The chain of attempted route matches, if any.
4) Something else?
Sergio Benitez