Fixed failing tests with command not found

[Chemaclass]

📚 Description

Fixes: #309 by @mkonig

Right now, when using a not found command in a test, this is ignored and makes the test pass as all good... This makes TDD impossible by definition.

We need to allow starting with a failing test writing what we want to have before having it.

This should fail! 🙃

🔖 Changes

• Check in the test_execution_result if contains "command not found" in such a case extract the error msg and render it as a failing test

Disclaimer: I didn't know how to write automated tests for this, because the logic is about making a test fail and I couldn't find a way to make a passing test when is failing... at least I share some screenshots. If you are reading this and you want to contribute adding an automated test for this change, please do! Thanks :)

✅ To-do list

• I updated the CHANGELOG.md to reflect the new feature or fix