Improve test coverage

[jakeberesford-palmetto]

Context
Our test coverage on this plugin is not great. It would be great to take the time to test as much of the code as we can.

Is your feature request related to a problem? Please describe.
No, this is an improvement that will help keep the codebase healthy in the long-run.

Describe the solution you'd like
Implement tests for the following (in loose priority order):

• dbt_plugin.py + plugins/dbt/init.py
• dbt_palm_utils.py
• sql_to_dbt_.py
• local_user_lookup.py
• Commands (this may be very tricky, take a shot but consider breaking this out to a separate issue if there are significant troubles writing meaningful tests around these)

Describe alternatives you've considered
Don't test the code, watch the project crumble over time.

Additional context
We are using pytest, there are already some tests around dbt_containerizer, look at palm-cli test_cli.py for reference in re. testing commands.

Is there an existing feature request for this?

• I have searched the existing issues