Issue loading rails 3 (server) after coming back from 3.1

Question

total noob to rails and am using the Hartl tutorial.

Got to chapter 4 (CSS, 4.1.2), everything seemed dandy, and ran into an issue getting

Answer 1

Per the answer to Trouble loading Rails Server (3.0.11, ruby 1.9.2), no such file to load -- sprockets/railtie (LoadError), you should remote Rails 3.1-specific lines from auto-generated files, mostly in config/.

One way to figure out what lines to remove is to compare your app to a fresh Rails 3.0 app using diff -r

Step 1: Create a clean Rails 3.0 app

$ rails --version
Rails 3.0.10

$ rails new fresh_app
      create  
      create  README
      create  Rakefile

Step 2: Use diff -r to compare the directories

$ diff -r hartl_tutorial/config fresh_app/config
diff -r hartl_tutorial/config/application.rb fresh_app/config/application.rb
5,10c5,7
< if defined?(Bundler)
<   # If you precompile assets before deploying to production, use this line
<   Bundler.require(*Rails.groups(:assets => %w(development test)))
<   # If you want your assets lazily compiled in production, use this line
<   # Bundler.require(:default, :assets, Rails.env)
< end
---
> # If you have a Gemfile, require the gems listed there, including any gems
> # you've limited to :test, :development, or :production.
> Bundler.require(:default, Rails.env) if defined?(Bundler)

In case you don't know how to read a diff, the basic idea is that lines starting with < are from one file while lines starting with > are from the other file.