Write tests for the CLI

[foobacca]

Currently there are no tests for the CLI code, that uses the click library.

The docs for writing tests for click apps is here: https://click.palletsprojects.com/en/stable/testing/

If we ever start relying on the CLI for more than basic testing we should probably actually write some tests.

[foobacca]

We now have basic happy path tests for the CSV commands - https://github.com/sortitionfoundation/sortition-algorithms/blob/main/tests/test_cli.py