dismissible form error message in Rails

gistfile1.haml

  - if @task.errors.any?
    = content_tag(:div, class: ["alert", "alert-danger", "alert-dismissible"], role: "alert", id: "error-explanation") do
      = content_tag(:button, class: "close", type: "button", "data-dismiss"=> "alert") do
        = content_tag(:span, escape_once("×"), "aria-hidden"=> "true")
        = content_tag(:span, "Close", class: "sr-only")
      %p= pluralize(@task.errors.count, "error") + " prohibited this user from being saved"
      %ul
        - @task.errors.full_messages.each do |msg|
          %li= msg