sourcemap references and CDNs result in 403 responses

wondering if - at least for CDN versions - there's a way of suppressing sourcemap references to files which aren't available (and result in 403 responses, which get silently absorbed by Chrome/Firefox/Safari dev tools but are - correctly? - exposed by Edge's dev tools) - see http://stackoverflow.com/questions/35142485/why-is-bootstrap-trying-to-load-less-files-in-edge/35151109

/cc @mdo @cvrebert