def test_export_without_format(self):
        self.client.login(username='admin', password='admin')
        # empty export
        resp = self.client.get(reverse('data_exports:export_view',
                               kwargs={'slug': self.empty_export.slug}))
        self.assertContains(resp, 'No columns where defined')
        # full export
        resp = self.client.get(reverse('data_exports:export_view',
                               kwargs={'slug': self.export.slug}))
        self.assertNotContains(resp, 'No columns where defined')
        for c in self.export.column_set.all():
            self.assertContains(resp, c.label if c.label else c)
Test that event dispatch works but removed listeners aren't called.
dataset/ETHPy150Open magopian/django-data-exports/data_exports/tests.py/ExportTest.test_export_without_format--crossover with--dataset/ETHPy150Open agronholm/apscheduler/tests/test_schedulers.py/TestBaseScheduler.test_add_remove_listener