LoadError: cannot load such file -- omniauth-twitter - ruby

Question

I'm trying to get OAuth2 working for my Sinatra app via OmniAuth but receive:
LoadError: cannot load such file -- omniauth-twitter
I'm following these examples, though they're a bit inconsistent
- http://recipes.sinatrarb.com/p/middleware/twitter_authentication_with_omniauth
app.rb
- https://github.com/intridea/omniauth/wiki/Sinatra-Example
The Sinatra Recipe tells me to put the builder within 'configure do' while the official example doesn't, but has 'use Rack::Session::Cookie'
I've scoured the net looking for good Sinatra OmniAuth examples, but it seems it favors Rails.
require "omniauth"
require "omniauth-twitter"
# OAuth2 configuration
use Rack::Session::Cookie
use OmniAuth::Builder do
provider :twitter, 'CONSUMER_KEY', 'CONSUMER_SECRET'
end
before do
# we do not want to redirect to twitter when the path info starts
# with /auth/
pass if request.path_info =~ /^\/auth\//
# /auth/twitter is captured by omniauth:
# when the path info matches /auth/twitter, omniauth will redirect to twitter
redirect to('/auth/twitter') unless current_user
end
get '/auth/twitter/callback' do
# probably you will need to create a user in the database too...
session[:uid] = env['omniauth.auth']['uid']
# this is the main endpoint to your application
redirect to('/')
end
get '/twitter' do
erb "<a href='/auth/twitter'>Sign in with Twitter</a>"
end
# Support for OAuth failure
get '/auth/failure' do
flash[:notice] = params[:message] # if using sinatra-flash or rack-flash
redirect '/'
end
The full error I get
Boot Error
Something went wrong while loading config.ru
LoadError: cannot load such file -- omniauth-twitter /usr/local/rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `require'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `block in require'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:236:in `load_dependency'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `require'
/Users/chadsakonchick/Projects/restlessnapkin/app.rb:11:in `<top (required)>'
config.ru:1:in `require'
config.ru:1:in `block in inner_app'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.5.2/lib/rack/builder.rb:55:in `instance_eval'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.5.2/lib/rack/builder.rb:55:in `initialize'
config.ru:1:in `new'
config.ru:1:in `inner_app'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:112:in `eval'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:112:in `inner_app'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:102:in `assemble_app'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:86:in `proceed_as_child'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:31:in `call!'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/loader.rb:18:in `call'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/shotgun-0.9/lib/shotgun/favicon.rb:12:in `call'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.5.2/lib/rack/builder.rb:138:in `call'
/usr/local/rvm/gems/ruby-1.9.3-p194/gems/rack-1.5.2/lib/rack/handler/webrick.rb:60:in `service'
/usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
/usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
/usr/local/rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'

Answer 1

Shotgun was the culprit. Works fine when I run 'ruby app.rb' from the terminal, but with shotgun I receive the error.

Answer 2

It looks like the omniauth-twitter gem isn't installed. For example:
> require "blahblahblah"
LoadError: cannot load such file -- blahblahblah
You need to gem install omniauth-twitter, include it in your gemspec if you're using bundler, or whatever makes sense in you project.