bug report on 'assume_role' usecase.

[no-brand]

found issue to should be fixed.

2021-04-19 13:31:42,577 | D | 40394 | MainThrea | [aws-cli-mfa] read mfa_device_arn (arn:aws:iam::${account-id}:mfa/${iam_user}) from ~/.aws/credentials
2021-04-19 13:31:44,121 | D | 40394 | MainThrea | [aws-cli-mfa] get-session-token is succeeded

Traceback (most recent call last):
  File "../aws-cli-mfa", line 6, in <module>
    module.run()
  File "../aws-cli-mfa/awsclimfa/main.py", line 80, in run
    args.assume_role = config[args.assume_profile]['assume_role_arn']
  File "../anaconda3/lib/python3.8/configparser.py", line 960, in __getitem__
    raise KeyError(key)
KeyError: None