Airflow 1.9 Error: "No module named `airflow.sensors`"

If you see this error pop up in the Airflow UI, it’s likely an inconsistency between where sensors are stored across Airflow versions.

In Airflow 1.9, sensors were in the operators folder and then moved out to the sensors folder in Airflow 1.10.

As long as you’re consistent with the version and where you call those sensors, you should be able to take care of that error.