You can convert the old-style decorator to a method decorator by using django.utils.decorators.method_decorator
like this:
from django.utils.decorators import method_decorator
...
class DashboardView(TemplateView):
template_name="omninectar/dashboard.html"
def get_context_data(self, **kwargs):
....
@method_decorator(active_and_login_required)
def dispatch(self, *args, **kwargs):
return super(DashboardView, self).dispatch(*args, **kwargs)
Related documentation is here: Introduction to Class-based Views