On recurly-client-python 3.x (3.4.2, python 3.8), hitting the API rate limit crashed the client instead of raising a proper rate-limit error. The traceback ended at self.rate_limit = int(self.__headers.get("X-RateLimit-Limit")) in response.py with TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'. Some responses (like 429s) don't include the X-RateLimit-Limit header, so .get() returned None and int(None) blew up. A contributor reproduced it in the test suite and confirmed the header parsing needed to be defensive.