class Gem::Resolver::InstallerSet

def ensure_required_rubygems_version_met(spec) # :nodoc:
  if rrgv = spec.required_rubygems_version
    unless rrgv.satisfied_by? Gem.rubygems_version
      rg_version = Gem::VERSION
      raise Gem::RuntimeRequirementNotMetError,
        "#{spec.full_name} requires RubyGems version #{rrgv}. The current RubyGems version is #{rg_version}. " \
        "Try 'gem update --system' to update RubyGems itself."
    end
  end
end