Change class rendering.

Instead of relying on an attribute that is not always there, check for the passed widget and decide which class to add.

hshassets/forms/utils.py

 from django.utils.safestring import mark_safe
 from django.utils.html import format_html, format_html_join
 from django.template import defaulttags
+from django.forms import widgets
 
 
 def render_form_field(field, label=None):
@@ -88,7 +89,12 @@ class BulmaFieldMarkup(object):
     @classmethod
     def select(cls, field, content):
         """Dropdowns have an extra wrapping <div class="select">"""
-        return cls.label(field.label, cls.div_control(format_html('<div class="select">{}</div>', content)))
+        if isinstance(field.field.widget, widgets.SelectMultiple):
+            css_classes = 'select is-multiple'
+        else:
+            css_classes = 'select'
+
+        return cls.label(field.label, cls.div_control(format_html('<div class="{}">{}</div>', css_classes, content)))
 
     @classmethod
     def checkbox(cls, field, content):
@@ -142,3 +148,10 @@ def render_form_errors(errors):
         """,
         error_tags=error_tags,
     )
+
+
+def instance_of(field_widget, widget_list):
+    for widget in widget_list:
+        if isinstance(field_widget, widget):
+            return True
+    return False