doesn't support 'aws_session_token' lines

[marcelser]

if you're using 2FA authentication in aws landing page you also have lines for "aws_session_token" in your .credentials file. The new implementation braks on "aws_session_token" lines.

Here's a short example of how my entries look like:
[ats-dev]
aws_access_key_id=abcdef
aws_secret_access_key=abcdef
aws_session_token=xxxxxxxx

[ats-prod]
aws_access_key_id=abcdef
aws_secret_access_key=abcdef
aws_session_token=xxxxxxx

please fix