AttributeError: 'NoneType' object has no attribute 'startswith' from get_user with 403 response

[mriedem]

Looks like the same root issue as #1399 but that was closed and I can't re-open it (not sure why it was closed).

This is with pygithub 1.55:

  File "/home/travis/virtualenv/python3.8.1/lib/python3.8/site-packages/github/MainClass.py", line 256, in get_user
    headers, data = self.__requester.requestJsonAndCheck(
  File "/home/travis/virtualenv/python3.8.1/lib/python3.8/site-packages/github/Requester.py", line 353, in requestJsonAndCheck
    return self.__check(
  File "/home/travis/virtualenv/python3.8.1/lib/python3.8/site-packages/github/Requester.py", line 378, in __check
    raise self.__createException(status, responseHeaders, output)
  File "/home/travis/virtualenv/python3.8.1/lib/python3.8/site-packages/github/Requester.py", line 418, in __createException
    elif status == 403 and output.get("message").startswith(
AttributeError: 'NoneType' object has no attribute 'startswith'

[EnricoMi]

@mriedem I have sketched out a fix for this and more possible situations where __createException may fail. Adds tests.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[mriedem]

Still hitting this with 1.58.

[suncle1993]

hitting this with 1.54.