fix: django.contrib.admin.util deprecated

newsbox_hvad/admin.py

@@ -6,7 +6,11 @@ from django.conf import settings
 from hvad.admin import TranslatableAdmin
 from hvad.forms import translatable_modelform_factory
 from django.utils.translation import ugettext_lazy as _
-from django.contrib.admin.util import flatten_fieldsets
+try:
+    from django.contrib.admin.utils import flatten_fieldsets
+except ImportError:
+    # django < 1.7
+    from django.contrib.admin.util import flatten_fieldsets
 from django.utils.functional import curry