Reached rate limit not handled correctly

[tomkoenecke]

  File "XX/python3.7/site-packages/webexteamssdk/restsession.py", line 345, in request
    check_response_code(response, erc)
  File "XX/python3.7/site-packages/webexteamssdk/utils.py", line 220, in check_response_code
    raise RateLimitError(response)
  File "XX/python3.7/site-packages/webexteamssdk/exceptions.py", line 141, in __init__
    self.retry_after = max(1, int(response.headers.get('Retry-After', 15)))
ValueError: invalid literal for int() with base 10: 'rand(30),add(30)'