class Bundler::LockfileParser

def warn_for_outdated_bundler_version
  return unless bundler_version
  prerelease_text = bundler_version.prerelease? ? " --pre" : ""
  current_version = Gem::Version.create(Bundler::VERSION)
  return unless current_version < bundler_version
  Bundler.ui.warn "Warning: the running version of Bundler (#{current_version}) is older " \
       "than the version that created the lockfile (#{bundler_version}). We suggest you to " \
       "upgrade to the version that created the lockfile by running `gem install " \
       "bundler:#{bundler_version}#{prerelease_text}`.\n"
end