Selenium get error message on required field

I use Selenium for a customer end actually i have a problem testing the error message on required field. I explain :

I work on a form with multiples input with the attributes required :

Form

The problem is : No html is generated with the error message. How did you get the actual text error ?

<select name="id_role" id="id_role" required="required" data-toggle="values" data-label-options="{&quot;Gestionnaire&quot;:[&quot;affiliation&quot;],&quot;Administrateur&quot;:[&quot;affiliation&quot;],&quot;Manageur&quot;:[&quot;affiliation&quot;],&quot;Utilisateur&quot;:[&quot;affiliation&quot;]}" 

class="form-control"> -- Choix -- Utilisateur Gestionnaire Manageur Entreprise Manageur Client

And second question, is that normal that the error is different in function of the browser ?

Thank you.