gulp watchで"Error: `libsass` bindings not found"というエラーが出たので．

# gulp watchで"Error: `libsass` bindings not found"というエラーが出たので，修正．

$ gulp watch
> [21:59:04] Using gulpfile /PATH/TO/gulpfile.js
> [21:59:04] Starting 'watch'...
> [21:59:04] Starting 'sass'...
> [21:59:04] Running Sass: resources/assets/sass/app.scss
> [21:59:04] 'sass' errored after 52 ms
> [21:59:04] Error: `libsass` bindings not found in /PATH/TO/node_modules/laravel-elixir/node_modules/gulp-sass/node_modules/node-sass/vendor/darwin-x64-44/binding.node.
> Try reinstalling `node-sass`?

$ npm rebuild node-sass
> ... (略)

# success
$ gulp watch
> ... (略)