change line 18 from ```on_updating_stylesheet``` to ```on_updated_stylesheet```

gistfile1.rb

module Compass
  module Configuration
    @callbacks_loaded = false
    # The helpers are available as methods on the Compass module. E.g. Compass.configuration
    module Helpers
      def configure_sass_plugin!
        puts "** configure_sass_plugin! **"
        require 'sass/plugin'
        config = sass_plugin_configuration
        locations = config.delete(:template_location)
        Sass::Plugin.options.merge!(config)
        locations.each do |sass_dir, css_dir|
          unless Sass::Plugin.engine_options[:load_paths].include?(sass_dir)
            Sass::Plugin.add_template_location sass_dir, css_dir
          end
        end
        unless @callbacks_loaded
          Sass::Plugin.on_updated_stylesheet do |sass_file, css_file|
            Compass.configuration.run_stylesheet_saved(css_file)
          end
          Sass::Plugin.on_compilation_error do |e, filename, css|
            Compass.configuration.run_stylesheet_error(filename, e.message)
          end
          @callbacks_loaded = true
        end
      end
    end
  end
end