No errors when missing config or missing profile for saml auth

[ElvenSpellmaker]

Describe the bug

When debugging with a Mac User, although I believe this applies to all.

If a config file is missing or missing the profile then the tool will open a blank window and exit 0.

To Reproduce
Steps to reproduce the behavior:

1. Have no config file or a missing profile
2. Run aws-cli-auth --verbose saml --cfg-section aws_foo_test -s

Expected behavior

1. Error explaining the config is missing or the profile is missing.
2. Exit non-zero.

Screenshots

Desktop (please complete the following information):

• OS: MacOS (not sure it matters though)
• Version 0.17.0
• Revision c08afec

Additional context

N/A

[dnitsch]

nice one - it needs further validation that used to happen only on the CLI.

[ElvenSpellmaker]

Implemented in #27