In that case, no its not available.
One comment though is that I don't use atom, but some "full fat" IDEs like VS or Eclipse have both actual compile errors from the build system and messages from the real time analysis system. That Atom error looks like one of the analysis errors, CSS doesn't have a "compiler" to build it.
Geany does not provide a pre-compile analysis system since for many languages Geany does not have enough information to do that analysis. Possibly for something like CSS it would be possible, but nobody has suggested how it would be done, let alone provided a PR.