class Gem::RequestSet::GemDependencyAPI

def ruby version, options = {}
  engine         = options[:engine]
  engine_version = options[:engine_version]
  raise ArgumentError,
        'you must specify engine_version along with the ruby engine' if
          engine and not engine_version
  return true if @installing
  unless RUBY_VERSION == version then
    message = "Your Ruby version is #{RUBY_VERSION}, " +
              "but your #{gem_deps_file} requires #{version}"
    raise Gem::RubyVersionMismatch, message
  end
  if engine and engine != Gem.ruby_engine then
    message = "Your ruby engine is #{Gem.ruby_engine}, " +
              "but your #{gem_deps_file} requires #{engine}"
    raise Gem::RubyVersionMismatch, message
  end
  if engine_version then
    my_engine_version = Object.const_get "#{Gem.ruby_engine.upcase}_VERSION"
    if engine_version != my_engine_version then
      message =
        "Your ruby engine version is #{Gem.ruby_engine} #{my_engine_version}, " +
        "but your #{gem_deps_file} requires #{engine} #{engine_version}"
      raise Gem::RubyVersionMismatch, message
    end
  end
  return true
end