_messages.html

{%- with messages = get_flashed_messages(with_categories=true) -%}
  {% if messages %}
    {% for category, message in messages %}
        {% if  category == 'success' or category == 'message' %}
            <div class="alert alert-success alert-dismissible" role="alert">
              <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">&times;</span></button>
              {{ message }}
            </div>
        {% elif category == 'error' %}
            <div class="alert alert-danger alert-dismissible" role="alert">
              <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">&times;</span></button>
              {{ message }}
            </div>
        {% else %}
            <div class="alert alert-success alert-dismissible" role="alert">
              <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">&times;</span></button>
              {{ category }} : {{ message }}
            </div>
        {% endif %}
    {% endfor %}
  {% endif %}
{%- endwith %}