Ensure that airflow modules are not imported too early in conftest (#17779)
Ensure that airflow modules are not imported too early in conftest (#17779)

If someone adds `import airflow` or any submodule in to conftest it will
cause airflow.settings and airflow.configuration to be imported and
initialized before we set the test env vars -- this leads to _some_
tests failing in bizarre ways.
mistercrunch/airflow,apache/incubator-airflow,bolkedebruin/airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,bolkedebruin/airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,apache/airflow,bolkedebruin/airflow,bolkedebruin/airflow,apache/airflow,apache/incubator-airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,apache/airflow,bolkedebruin/airflow,nathanielvarona/airflow,nathanielvarona/airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow,mistercrunch/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,mistercrunch/airflow,apache/incubator-airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,apache/airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,mistercrunch/airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,apache/airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow