build.py: fix to support Python 3.8.2
build.py: fix to support Python 3.8.2

This was broken in [3.8.1 RC1], and fixed back in [3.8.3 RC1].
Ref: https://bugs.python.org/issue39517

[3.8.1 RC1]:https://docs.python.org/3/whatsnew/changelog.html#python-3-8-1-release-candidate-1
[3.8.3 RC1]:https://docs.python.org/3/whatsnew/changelog.html#python-3-8-3-release-candidate-1

McBen/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion