[AIRFLOW-1799] Fix logging line which raises errors
[AIRFLOW-1799] Fix logging line which raises errors

Closes #2777 from ryancbuckley/log-syntax-fix

(cherry picked from commit f14f8558be08b8175c0f88f8cf02be3e7583151f)
Signed-off-by: Bolke de Bruin <17f52a69a3ba26c79c8a88ef8c1f26312d9cbf0e@xs4all.nl>

Twistbioscience/incubator-airflow,Twistbioscience/incubator-airflow,Twistbioscience/incubator-airflow,Twistbioscience/incubator-airflow