app/templates/_flash_messages.html

{% with messages = get_flashed_messages(with_categories=true) %} {% if messages
%}
<div class="container-fluid px-0 mb-4">
  {% for category, message in messages %}
  <div
    class="alert alert-{{ category }} alert-dismissible fade show"
    role="alert"
  >
    {{ message }}
    <button
      type="button"
      class="btn-close"
      data-bs-dismiss="alert"
      aria-label="Close"
    ></button>
  </div>
  {% endfor %}
</div>
{% endif %} {% endwith %}