ihatemoney_ynh/budget/templates/member_form.html

{% for errors in form.errors.values() %}
    {% for error in errors %}
        <p class="error">{{error}}</p>
    {% endfor %}
{% endfor %}
<form action="{{ url_for("add_member", project_id=project.id) }}" method="post">
    {{ form.hidden_tag() }}
    <p>{{ form.name.label }}<br /> {{ form.name }}</p>
    <p>{{ form.submit }}</p>
</form>