Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes #xyz
• (If applicable) Documentation has been added / updated (for bug fixes / features).
• (If applicable) Tests have been added.
• This PR does not seem to break the templates.
• HISTORY.rst has been updated (with summary of main changes).
  • Link to issue (:issue:number) and pull request (:pull:number) has been added.

What kind of change does this PR introduce?

• Catches and remits the error when translation files have not been compiled. The new error tells the user what to do. In theory, this happens only once when someone pulls the *.po files for the first time. This does not detect if the compiled translations are outdate. It also only happens if xscen was installed with pip install -e ..
• Add a note in the Good To Know page about updating the compiled translations when using xscen from source.
• Add a line in History about the translation PR.

Does this PR introduce a breaking change?

No