def handle_http_exception(self, e):
        """Handles an HTTP exception.  By default this will invoke the
        registered error handlers and fall back to returning the
        exception as response.

        .. versionadded:: 0.3
        """
        handlers = self.error_handler_spec.get(request.blueprint)
        # Proxy exceptions don't have error codes.  We want to always return
        # those unchanged as errors
        if e.code is None:
            return e
        if handlers and e.code in handlers:
            handler = handlers[e.code]
        else:
            handler = self.error_handler_spec[None].get(e.code)
        if handler is None:
            return e
        return handler(e)