This error means that browser can’t find the file pointed here: https://github.com/pkp/healthSciences/blob/master/libs/bootstrap.min.css#L7
Source map files, like
bootstrap.min.css.map, are generated automatically during files minification/compiling process. They actually are not needed for the production, but at the same time occupy 3 times more disk space than ones which they are mapping. That’s why I don’t include them in the release.
If you want just to remove that message, you can either remove comments like
/*# sourceMappingURL=bootstrap.min.css.map */ in
popper.min.js or download source map files from a Bootstrap 4.1.3 release and put them inside