Fix front end tools error message

[lassemoldrup]

Purpose

Closes #135.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.

[DOBEN]

You can run yarn lint --fix and yarn fmt before pushing the code to have your code linted (avoids the failing CI pipeline).