'Inspect the Authorization HTTP header, and return a deferred which,
when fired after successful authentication, will return an authorized
C{Avatar}. On authentication failure, an C{UnauthorizedResource} will
be returned, essentially halting further dispatch on the wrapped
resource and all children'

def getChildWithDefault(self, path, request):

    request.postpath.insert(0, request.prepath.pop())
    return self._authorizedResource(request)
