You need to show the errors in the template. Crispy forms has a template you can include for the errors: {% include 'bootstrap3/layout/help_text_and_errors.html' %}
(if you're using bootstrap 3).
So your custom template might be like this:
<div id="div_{{ field.auto_id }}" class="form-group{% if field.errors %} has-error{% endif %}">
{% if field.label and form_show_labels %}
<label for="{{ field.id_for_label }}" class="control-label {{ label_class }}{% if field.field.required %} requiredField{% endif %}">
{{ field.label|safe }}{% if field.field.required %}<span class="asteriskField">*</span>{% endif %}
</label>
{% endif %}
<div class="controls col-xs-8 col-md-9 col-lg-9">
{% crispy_field field %}
{% include 'bootstrap3/layout/help_text_and_errors.html' %}
</div>
</div>