tap/app/views/application/_errors.html.erb

<% if model.errors.any? %>
    <div class="panel panel-danger form-errors">
    <div class="panel-heading">
      <%= pluralize(model.errors.count, "error") %> prohibited this <%= model.class.name.downcase %> from being saved:
    </div>
    <div class="panel-body">
      <ul>
        <% model.errors.full_messages.each do |msg| %>
            <li><%= msg %></li>
        <% end %>
      </ul>
    </div>
  </div>
<% end %>