[robert-boehnke]

If I had to guess, the no break space that macOS has on [alt]-[space]: " ".

EDIT: Hmm, that doesn't seem to be it, here's the commit in question https://github.com/alphagov/govuk-puppet/commit/63b36f93bf75...

[bassdigit]

It IS the no-break space. The hex UTF-8 representation of it is C2A0; you can find that sequence in original version of the file.