set_error_serializer

https://falcon.readthedocs.io/en/latest/api/api.html#falcon.API.set_error_serializer

def my_serializer(req, resp, exception):
    representation = None

    preferred = req.client_prefers((falcon.MEDIA_YAML, falcon.MEDIA_JSON))

    if preferred is not None:
        if preferred == falcon.MEDIA_JSON:
            resp.data = exception.to_json()
        else:
            resp.text = yaml.dump(exception.to_dict(), encoding=None)
        resp.content_type = preferred

    resp.append_header('Vary', 'Accept')


app.set_error_serializer(my_serializer)  # 错误输出xml转换成json