cubicweb #2517095 ldaputils raise ValidationError(entity) instead of entity.eid [done]

which may be problematic in some cases. See #2509729

prioritynormal
typebug
done in3.15.6
load0.100
load left0.000
closed by#bc74608d2003 [ldaputils] should use entity.eid instead of entity on raising ValidationError. closes #2517095