def compile_assets
      sources_with_assets.each do |file|
        source = File.read file
        assets.each { |a| a.update_source! source }
        Utils.write_to_file source, file, preserve: true
      end
      self
    end
def compile_assets
      sources_with_assets.each do |file|
        source = File.read file
        assets.each { |a| a.update_source! source }
        Utils.write_to_file source, file, preserve: true
      end
      self
    end
Finds all assets in {#sources_with_assets} and
 generates the assets and updates the sources.
 @return [Environment] the current environment instance