Formatting Rails form elements for Twitter Bootstrap error validation

application.rb

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  html = %(<div class="field_with_errors">#{html_tag}</div>).html_safe
  # add nokogiri gem to Gemfile
  
  form_fields = [
    'textarea',
    'input',
    'select'
  ]

  elements = Nokogiri::HTML::DocumentFragment.parse(html_tag).css "label, " + form_fields.join(', ')
  
  elements.each do |e|
    if e.node_name.eql? 'label'
      html = %(<div class="control-group error">#{e}</div>).html_safe
    elsif form_fields.include? e.node_name
      if instance.error_message.kind_of?(Array)
        html = %(<div class="control-group error">#{html_tag}<span class="help-inline">&nbsp;#{instance.error_message.join(',')}</span></div>).html_safe
      else
        html = %(<div class="control-group error">#{html_tag}<span class="help-inline">&nbsp;#{instance.error_message}</span></div>).html_safe
      end
    end
  end
  html
end

your_controller.css.scss

// Place all the styles related to the YourController controller here.
// They will automatically be included in application.css.
// You can use Sass (SCSS) here: http://sass-lang.com/

form .clearfix:before, form .clearfix:after {
  display: inline;
}

Any solution for adding a class in grandfather div?