Unable to start Rails Server after updating to Rails 4

Question

I just upgraded to rails 4, and when I run rails s, I get the output pasted below. I've made sure that my gems are up to date by running bundle install and bundle update, and I've consulted other SO pages with the same issues, but can't figure out what's going wrong with mine. Please help!

Codys-MacBook-Pro:club_website codyma$ rails s
=> Booting WEBrick
=> Rails 4.0.1 application starting in development on http://0.0.0.0:3000
=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
Exiting
/Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/actionpack-        4.0.1/lib/action_dispatch/middleware/stack.rb:107:in `delete': can't modify frozen Array (RuntimeError)
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/actionpack-    4.0.1/lib/action_dispatch/middleware/stack.rb:107:in `delete'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/sass-rails-4.0.1/lib/sass/rails/railtie.rb:29:in `block in <class:Railtie>'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-4.0.1/lib/active_support/lazy_load_hooks.rb:36:in `call'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-4.0.1/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-4.0.1/lib/active_support/lazy_load_hooks.rb:45:in `block in run_load_hooks'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-4.0.1/lib/active_support/lazy_load_hooks.rb:44:in `each'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-4.0.1/lib/active_support/lazy_load_hooks.rb:44:in `run_load_hooks'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/application/finisher.rb:62:in `block in <module:Finisher>'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/initializable.rb:30:in `instance_exec'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/initializable.rb:30:in `run'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/initializable.rb:55:in `block in run_initializers'
from /Users/codyma/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/tsort.rb:150:in `block in tsort_each'
from /Users/codyma/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/tsort.rb:183:in `block (2 levels) in each_strongly_connected_component'
from /Users/codyma/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/tsort.rb:219:in `each_strongly_connected_component_from'
from /Users/codyma/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/tsort.rb:182:in `block in each_strongly_connected_component'
from /Users/codyma/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/tsort.rb:180:in `each'
from /Users/codyma/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/tsort.rb:180:in `each_strongly_connected_component'
from /Users/codyma/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/tsort.rb:148:in `tsort_each'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/initializable.rb:54:in `run_initializers'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/application.rb:215:in `initialize!'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/railtie/configurable.rb:30:in `method_missing'
from /Users/codyma/Development/club_website/config/environment.rb:5:in `<top (required)>'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:229:in `require'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:229:in `block in require'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:214:in `load_dependency'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/activesupport-4.0.1/lib/active_support/dependencies.rb:229:in `require'
from /Users/codyma/Development/club_website/config.ru:3:in `block in <main>'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/rack-1.5.2/lib/rack/builder.rb:55:in `instance_eval'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/rack-1.5.2/lib/rack/builder.rb:55:in `initialize'
from /Users/codyma/Development/club_website/config.ru:in `new'
from /Users/codyma/Development/club_website/config.ru:in `<main>'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/rack-1.5.2/lib/rack/builder.rb:49:in `eval'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/rack-1.5.2/lib/rack/builder.rb:49:in `new_from_string'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/rack-1.5.2/lib/rack/builder.rb:40:in `parse_file'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/rack-1.5.2/lib/rack/server.rb:277:in `build_app_and_options_from_config'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/rack-1.5.2/lib/rack/server.rb:199:in `app'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/commands/server.rb:48:in `app'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/rack-1.5.2/lib/rack/server.rb:314:in `wrapped_app'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/commands/server.rb:75:in `start'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/commands.rb:76:in `block in <top (required)>'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/commands.rb:71:in `tap'
from /Users/codyma/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.1/lib/rails/commands.rb:71:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'

Answer 1

Maybe there's an error in your config.ru file.

For Rails 3:

# This file is used by Rack-based servers to start the application.

require ::File.expand_path('../config/environment',  __FILE__)
run YouApp::Application

For Rails 4:

# This file is used by Rack-based servers to start the application.

require ::File.expand_path('../config/environment',  __FILE__)
run Rails.application