UnboundLocalError when Okta password is expired

[kirilyer]

When trying to refresh AWS tokens using an expired Okta password an exception is raised instead of a friendly message to the user.

 > okta-awscli -f -v -d -P <password>
DEBUG - Setting AWS role to arn:aws:iam::<account>:role/<role>
DEBUG - Setting AWS partition to AwsPartition.AWS
DEBUG - Setting AWS profile to default
INFO - App Link set as: https://<org>.okta.com/home/amazon_aws/<...>
INFO - Authenticating to: <org>.okta.com
INFO - Authenticating as: <email>
Traceback (most recent call last):
  File "/path/to/venv/bin/okta-awscli", line 33, in <module>
    sys.exit(load_entry_point('okta-awscli==0.5.4', 'console_scripts', 'okta-awscli')())
  File "/path/to/venv/lib/python3.8/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/path/to/venv/lib/python3.8/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/path/to/venv/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/path/to/venv/lib/python3.8/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/path/to/venv/lib/python3.8/site-packages/oktaawscli/okta_awscli.py", line 141, in main
    get_credentials(
  File "/path/to/venv/lib/python3.8/site-packages/oktaawscli/okta_awscli.py", line 36, in get_credentials
    _, assertion = okta.get_assertion()
  File "/path/to/venv/lib/python3.8/site-packages/oktaawscli/okta_auth.py", line 156, in get_assertion
    self.session_token = self.primary_auth()
  File "/path/to/venv/lib/python3.8/site-packages/oktaawscli/okta_auth.py", line 78, in primary_auth
    return session_token
UnboundLocalError: local variable 'session_token' referenced before assignment

To Reproduce

1. Have your Okta password expire.
2. Try to refresh tokens.
3. Get an exception.

Expected behavior
I would expect to see an error saying the Okta password is expired instead of an exception stack trace.

Output
see above.

Environment (please complete the following information):

• OS: MacOS Monterey 12.3.1
• okta-awscli version: 0.5.4
• Python 3.8.2