Review on GPL fix required for 1.10 release

[Bolke de Bruin]

Hi Committers et al,

Can I get a review on https://github.com/apache/incubator-airflow/pull/3660 
<https://github.com/apache/incubator-airflow/pull/3660>

it is required to be able to restart the voting process for 1.10.

Thx
Bolke