readFile'd content only visible from hugo server or local builds

I have a project I’m trying to use Hugo with (https://github.com/melt-umn/monto-v3-draft) with a custom shortcode, include-json:

{{ printf "```json\n%s\n```" (readFile (.Get 0)) | markdownify }}

When I use hugo or hugo server, the page appears correctly:

hugo:

hugo server:

http://i.imgur.com/kBYmJif.png (new user image limit)

However, when Travis builds it, the JSON files are not properly included:

http://i.imgur.com/JuGF9xi.png (new user image limit)

I don’t get any relevant-sounding warnings, either…

This is definitely highlighting-related – after disabling highlighting, the JSON shows up. pygmentize is in the PATH, though: https://travis-ci.org/melt-umn/monto-v3-draft/builds/243448401#L386