Set EXIT_CODE for all failures

[paul121]

Description

Closes: #71

It seems the errors are being caught but not setting this global EXIT_CODE variable

---

Author Checklist

All items are required. Please add a note to the item if the item is not applicable and please add links to any relevant follow up issues.

I have...

• [x] provided a link to the relevant issue or specification
• [x] reviewed "Files changed" and left comments if necessary

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add your handle next to the items reviewed if you only reviewed selected items.

I have...

• [ ] confirmed all author checklist items have been addressed
• [ ] reviewed code correctness and readability
• [ ] reviewed documentation is accurate
• [ ] manually tested (if applicable)

[blushi]

Thanks for your contribution @paul121!