Lookup a config field and return its value, first checking the
            route.config, then route.app.config.

def get_config(self, key, default=None):
        """ Lookup a config field and return its value, first checking the
            route.config, then route.app.config."""
        depr(0, 13, "Route.get_config() is deprectated.",
                    "The Route.config property already includes values from the"
                    " application config for missing keys. Access it directly.")
        return self.config.get(key, default)