How to check for validation errors in onsuccess of BootsFaces commandButton?

Question

I'm using Bootsfaces, and I've a component defined like:

<b:commandButton type="button" styleClass="btn-sm"
   value="ACTION"
   update="idC1 idC2" onsuccess="something()"
    actionListener="#{myBean.myaction}" />

What I want is that myaction() force an Ajax error, in order to assure that something() is run

void myaction() {
if (condition) {
     success();
else 
     notsuccess();
}

As far as I can see validation errors dont cause ajax error. Right? Onsuccess script is run even if I throw a Faces validation exception. So it must exist another way.

Anybody can help me?