Ensure tests are working in all environments by running them in US english

[Madeorsk]

Problem

Some tests were not working locally as I have a machine configured in a different language than

Solution

Override environment to always use LANG=en_US.UTF-8 to run tests in a consistent environment.

How To Test

LANG=fr_FR.UTF-8 make test and it's still working.

Additional Checks

• [X] The PR targets master for a bugfix or a documentation fix, or next for a feature
• ~[ ] The PR includes unit tests (if not possible, describe why)~
• ~[ ] The PR includes one or several stories (if not possible, describe why)~
• [X] The documentation is up to date