Display Resourceable errors

action.html.erb

<% if @category.errors.any? %>
  <div class="alert alert-block alert-error">
    <h4><%= pluralize( @category.errors.count, 'error' ) %> prohibited this Category from being saved:</h4>

    <ul>
    <% @category.errors.full_messages.each do |msg| %>
      <li><%= msg %></li>
    <% end %>
    </ul>
  </div>
<% end %>