fix(cli): gracefully output configuration validation errors

[codejedi365]

Purpose

Improve handling of exceptions to provide a useful message to user without stack trace

Rationale

If a user puts in an invalid configuration setting, the configuration validator will throw a ValidationException that we do not catch gracefully. This causes python to dump a stack trace and hide the pretty ValidationError that pydantic provides by default.

In order to set up the test appropriately, I found it useful to add a fixture that will modify the configuration file accordingly. Meanwhile, I noticed that the implementation of example project was a bit fragile as exceptions are not handled well with generators or context managers unless explicitly using try/finally. With this modification I was able to align it more with the setup/teardown generator style fixtures as pytest recommends.

How I tested

Created a command line test that modifies the configuration file to be incorrect before executing the version command. It evaluates the exit code and the stderr message to the user that there is a validation error and which component.

How to verify

git fetch origin pull/772/head:pr/772

# checkout the PR as a detached HEAD state with only the unit tests
git checkout pr/772~1 --detach

# execute tests, should fail
pytest tests/ -k test_errors_when_config_file_invalid_configuration

# update to the HEAD of the PR (with fixes)
git merge --ff-only pr/772

# run pytest again (looking for success)
pytest tests/ -k test_errors_when_config_file_invalid_configuration

# run entire test suite for regression testing
PYTHONHASHSEED=123456 pytest tests/

[codejedi365]

@bernardcooke53, @relekang, would you mind doing a review?

[bernardcooke53]

LGTM, thanks @codejedi365 🎉