以前在 heroku 部署 rails3.2.12 从没遇到这种问题，昨天在部署应用时，heroku 报错

DEPRECATION WARNING: You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/1/4/rails-3-2-0-rc2-has-been-released. (called from at /app/config/environment.rb:8)

app/vendor/bundle/ruby/1.9.1/gems/activesupport- 3.2.12/lib/active_support/dependencies.rb:317:in rescue in depend_on': No such file to load -- spec_helper (LoadError)

然后在 stackoverflow 上发现这个解释：

Response from Heroku: Lincoln, Jan 29 08:32 pm (PST): Hi, they are deprecated in 3.2, but will continue to function correctly until Rails 4.0 is released. We are aware of this and working on an updated system for this, no current ETA but I'd imagine definitely before 4.0 ships. Cheers, - Linc

在本地跑没有任何问题。生产环境也使用了 pg。