エラー文
DEPRECATION WARNING: Sprockets method `register_engine` is deprecated. Please register a mime type using `register_mime_type` then use `register_compressor` or `register_transformer`. https://github.com/rails/sprockets/blob/master/guides/extending_sprockets.md#supporting-all-versions-of-sprockets-in-processors (called from block in <class:Railtie> at /Library/Ruby/Gems/2.3.0/gems/less-rails-2.8.0/lib/less/rails/railtie.rb:16) DEPRECATION WARNING: You are using a deprecated processor interface Less::Rails::ImportProcessor. Please update your processor interface: https://github.com/rails/sprockets/blob/master/guides/extending_sprockets.md#supporting-all-versions-of-sprockets-in-processors (called from block in <class:Railtie> at /Library/Ruby/Gems/2.3.0/gems/less-rails-2.8.0/lib/less/rails/railtie.rb:21)
https://teratail.com/questions/57406
こちらの記事は読みましたが解決には至りませんでした
URLは https://teratail.com/help/question-tips#questionTips3-7 の [コード] ではなく、 [リンク] に修正してください。