我不得不将我的 rails 版本从 5 更新到 6，在此之前一切正常。
问题只发生在 capistrano 上......当我运行时rake assets:precompile，即使使用新版本，一切也能正常工作。
这是错误：
deploy:assets:precompile
01 $HOME/.rbenv/bin/rbenv exec bundle exec rake assets:precompile
01 warning: parser/current is loading parser/ruby25, which recognizes
01 warning: 2.5.7-compliant syntax, but you are running 2.5.3.
01 warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
yarn install v1.16.0
[1/4] Resolving packages...
?
success Already up-to-date.
Done in 0.71s.
01 Warning: you are using an unstable release of Node.js (v11.15.0). If you encounter issues with Node.js, consider switching to an Active LTS release. …