Warn, not crash, when file from JSB not found.

        if File.directory?(fname)

          Dir[fname+"/**/*.{js,css,scss}"].each {|f| @input_files << f }

        elsif fname =~ /\.jsb3$/

          @input_files += extract_jsb_files(fname)

          extract_jsb_files(fname).each {|fn| read_filenames(fn) }

        else

          @input_files << fname

        end