Jean Helsinki

Airflow 2.x support: * airflow.operators.dummy_operator -> airflow.operators.dummy * airflow.operators.bash_operator -> airflow.operators.bash * airflow.sensors.http_sensor -> airflow.providers.http.sensors.http * tests: fix yaml.load warning airflow-declarative/tests/test_good_dags.py:49: YAMLLoadWarning: calling yaml.load() without Loader=... is deprecated, as the...

We use custom python3.6 build from [ppa](https://launchpad.net/~deadsnakes/+archive/ubuntu/ppa), because our production distro (ubuntu 16.04) not include it. This custom build not contain metapackage `python3-all`, it's fine, but stdeb always add this...