devise helper to list errors in alert box

deviseerrors.rb

module DeviseHelper
  def devise_error_messages!
    return "" if resource.errors.empty?

    messages = resource.errors.full_messages.map { |msg| 
      content_tag :li do 
        content_tag(:div, ' ', :class=>'glyphicon glyphicon-exclamation-sign') +
        content_tag(:span, ' '+msg)
      end
    }.join
    sentence = I18n.t("errors.messages.not_saved",
                      :count => resource.errors.count,
                      :resource => resource.class.model_name.human.downcase)

    html = <<-HTML
    <div>
      <ul class='alert alert-danger'>#{messages}</ul>
    </div>
    HTML

    html.html_safe
  end

  def devise_error_messages?
    resource.errors.empty? ? false : true
  end

end