'Missing application settings raises ImproperlyConfigured.'

def test_missing_setting(self):

    application_id = 'my_fcm_app'
    PUSH_SETTINGS = {'APPLICATIONS': {application_id: {'PLATFORM': 'FCM'}}}
    with self.assertRaises(ImproperlyConfigured) as ic:
        AppConfig(PUSH_SETTINGS)
    self.assertEqual(str(ic.exception), "PUSH_NOTIFICATIONS_SETTINGS.APPLICATIONS['my_fcm_app']['API_KEY']    is    missing.")
