Replaced ugettext and ugettext_lazy with gettext and gettext_lazy

ugettext and ugettext_lazy were deprecated in Django 3 and will be
removed in Django 4.

dav_events/views/actions.py

@@ -2,7 +2,7 @@ import logging
 from django.contrib import messages
 from django.contrib.auth import login
 from django.http import HttpResponseRedirect
-from django.utils.translation import ugettext as _
+from django.utils.translation import gettext as _
 from django.views import generic
 
 from .. import models