gistfile1.rb

require 'singleton'

class Configuration
  include Singleton

  def initialize
    config_file = File.join(RAILS_ROOT, "config", "application.yml")

    if File.exists?(config_file)
      config = YAML.load(File.read(config_file))[RAILS_ENV]

      config.keys.each do |key|
        attr_accessor key
        send "#{key}=", config[key]
      end
    end
  end
end

gistfile2.rb

home/camilo/Development/ontoworks/accounts/ontoworks-accounts/lib/configuration.rb:13:in `initialize': undefined method `attr_accessor' for #<Configuration:0x7fc5a87e16c8> (NoMethodError)