Using the shopify_app gem and require method problems

Just came across a perculiar problem that took a while to figure out so I thought I should document it for prosperity.

Situation was that I was trying to do a capistrano deploy using the shopify-app gem and was getting an error: NoMethodError: super: no superclass method `require' for main:Object.

The stack trace looked like this:

  * executing "cd /home/sva/app/releases/20140712202310 && bundle exec rake RAILS_ENV=production  db:migrate"
    servers: ["**.**.**.163"]
    [**.**.**.163] executing command
 ** [out :: **.**.**.163] rake aborted!
 ** [out :: **.**.**.163] NoMethodError: super: no superclass method `require' for main:Object
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:251:in `require'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:236:in `load_dependency'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:251:in `require'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/core_ext/module/attribute_accessors.rb:35:in `to_proc'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/shopify_api-3.0.3/lib/shopify_api/resources.rb:2:in `glob'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/shopify_api-3.0.3/lib/shopify_api/resources.rb:2
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:251:in `require'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:251:in `require'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:236:in `load_dependency'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:251:in `require'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/shopify_api-3.0.3/lib/shopify_api.rb:22
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:251:in `require'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:251:in `require'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:236:in `load_dependency'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/activesupport-3.2.19/lib/active_support/dependencies.rb:251:in `require'
 ** [out :: **.**.**.163] /home/sva/app/shared/bundle/ruby/1.8/gems/shopify_app-3.0.4/lib/shopify_app.rb:1
 ** [out :: **.**.**.163] /home/sva/app/releases/20140712202310/config/application.rb:7
 ** [out :: **.**.**.163] /home/sva/app/releases/20140712202310/Rakefile:5:in `require'
 ** [out :: **.**.**.163] /home/sva/app/releases/20140712202310/Rakefile:5
 ** [out :: **.**.**.163] (See full trace by running task with --trace)

The fix turned out to be simple, but unfortunately I don't know exactly how it fixed it. I moved the location of the shopify-app gem to just after where rails was defined. I suspect this had something to do with monkey patching.

The working (truncated) Gemfile looks like this:

source 'http://rubygems.org'

gem 'rails', '~> 3.2.0'
gem 'shopify_app', '~> 3.0.4' # ruby 1.8.7 compatible
...

If anyone can shed some more light on why moving it higher up fixes it please let me know via the comments.