Build: Fix sandbox publish script

[yannbf]

Closes #

What I did

The sandbox publish script was not working because of a missing " in the command that generated the message 😮‍💨 however the script logs were just saying "nothing to commit", therefore showing a false success. The sandboxes repo hasn't been updated for a couple days already, so we are not testing the latest alphas.

This PR fixes that + improves the error handling so we don't fall into this situation again!

How to test

I tested this extensively, it's a little troublesome to do it locally without impacting the sandboxes repo so please reach out and I can give all details to do so if you'd like

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]