Form theming for error class on row

form.html.twig

{% block field_row %}
{% spaceless %}
    <div {{ errors|length > 0 ? 'class="error"' : '' }}>
        {{ form_label(form, label|default(null)) }}
        {{ form_errors(form) }}
        {{ form_widget(form) }}
    </div>
{% endspaceless %}
{% endblock field_row %}