[django] Django Forms: if not valid, show form with error message

This answer is correct but has a problem: fields not defined. If you have more then one field, you can not recognize which one has error.

with this change you can display field name:

{% if form.errors %}
    {% for field in form %}
        {% for error in field.errors %}
            <div class="alert alert-danger">
                <strong>{{ field.label }}</strong><span>{{ error|escape }}</strong>
            </div>
        {% endfor %}
    {% endfor %}
    {% for error in form.non_field_errors %}
        <div class="alert alert-danger">
            <strong>{{ error|escape }}</strong>
        </div>
    {% endfor %}
{% endif %}