{% set flashTypes = {
    'success': {'class': 'alert-success', 'strong': 'Bravo !'},
    'warning': {'class': 'alert-warning', 'strong': 'Attention !'},
    'error': {'class': 'alert-danger', 'strong': 'Erreur !'}
} %}

{% for type, config in flashTypes %}
    {% for message in app.flashes(type) %}
        <div class="alert {{ config.class }} alert-dismissible text-center mt-4 mx-auto" role="alert">
            <button type="button" class="close" data-dismiss="alert" aria-label="Close">
                <span aria-hidden="true">&times;</span>
            </button>
            <strong>{{ config.strong }}</strong> {{ message }}
        </div>
    {% endfor %}
{% endfor %}