TWIG

Hello,
I use twig for one of my app, but still encounter some difficulties,
In the same form, when error on "fichier" field occurs,
this, prints errors :

PHP Code:

{% if validation == false %}
<div class="notification is-danger">
{{ validation_list_errors() }}
</div>
{% endif %} 


While this does not :

PHP Code:

  {% if validation.hasError("fichier") %}
      <div class="notification is-danger">{{ validation.getError("fichier") }}</div>
  {% endif %} 


can someone see the mistake I make ?