class RuboCop::ConfigValidator

def check_target_ruby
  return if target_ruby.supported?
  source = target_ruby.source
  last_version = target_ruby.rubocop_version_with_support
  msg = if last_version
          "RuboCop found unsupported Ruby version #{target_ruby_version} " \
            "in #{source}. #{target_ruby_version}-compatible " \
            "analysis was dropped after version #{last_version}."
        else
          'RuboCop found unknown Ruby version ' \
            "#{target_ruby_version.inspect} in #{source}."
        end
  msg += "\nSupported versions: #{TargetRuby.supported_versions.join(', ')}"
  raise ValidationError, msg
end