
**Apache Airflow version**:
2.0.0

**Environment**:

- **OS** (e.g. from /etc/os-release): Ubuntu 20.04 LTS
- **Python version**: 3.8
- **Kernel** (e.g. `uname -a`): x86_64 x86_64 x86_64 GNU/Linux 5.4.0-58-generic #64-Ubuntu
- **Install tools**: pip


**What happened**:

Airflow 2.0 does not send metrics to statsD.

I configure Airflow with official documentation (https://airflow.apache.org/docs/apache-airflow/stable/logging-monitoring/metrics.html) and by this article https://dstan.medium.com/run-airflow-statsd-grafana-locally-16b372c86524 (but I used port 8125). 

I turned on statsD:

```ini
statsd_on = True
statsd_host = localhost
statsd_port = 8125
statsd_prefix = airflow
```

But I do not see airflow metrics at http://localhost:9102/metrics (statsD metrics endpoint).

---

P.S. I noticed this error just using Airflow 2.0. In version 1.10.13 everything is ok in the same environment.

Thank you for advance.



tests/core/test_stats.py
importlib.reload(airflow.stats)
        airflow.stats.Stats.incr("dummy_key")
        assert airflow.stats.Stats.statsd.incr_calls == 1
    @conf_vars(
        {
            ("metrics", "statsd_on"): "True",
            ("metrics", "statsd_custom_client_path"): "tests.core.test_stats.InvalidCustomStatsd",
        }
    )
    def test_load_invalid_custom_stats_client(self):
        with pytest.raises(
            AirflowConfigException,
            match=re.escape(
                'Your custom Statsd client must extend the statsd.'
                'StatsClient in order to ensure backwards compatibility.'
            ),
        ):
            importlib.reload(airflow.stats)
    def tearDown(self) -> None:
        
        importlib.reload(airflow.stats)
class TestDogStats(unittest.TestCase):