gistfile1.rb

= form_for @user2 do |f|
  - if @user2.errors.any?
    #error_explanation
      %h2= "#{pluralize(@user2.errors.count, "error")} prohibited this user2 from being saved:"
      %ul
        - @user2.errors.full_messages.each do |msg|
          %li= msg

  .field
    = f.label :nome
    = f.text_field :nome

  %br
    = f.file_field :avatar
  .actions
    = f.submit 'Save'