app/views/foreman_docker/common_parameters/_dns_entry.html.erb
<tr class="fields form-group <%= 'has-error' if f.object.errors.any? %>">
<td><%= f.text_field(:key, :class => "form-control",
:placeholder => _("DNS e.g. 8.8.8.8")) %></td>
<td style='vertical-align: middle' class='text-center'>
<span class="help-block">
<%= link_to_remove_fields('', f) %>
</span>
</td>
<span class="help-block">
<%= f.object.errors.full_messages.to_sentence %>
</span>
</tr>