'Add a route to the proxy.
**Subclasses must define this method**
Args:
routespec (str): A URL prefix ([host]/path/) for which this route will be matched,
e.g. host.name/path/
target (str): A full URL that will be the target of this route.
data (dict): A JSONable dict that will be associated with this route, and will
be returned when retrieving information about this route.
Will raise an appropriate Exception (FIXME: find what?) if the route could
not be added.
The proxy implementation should also have a way to associate the fact that a
route came from JupyterHub.'

@gen.coroutine
def add_route(self, routespec, target, data):

    pass
