failing:

root@b27e0e37a4b9:/vsts# python3 --version
Python 3.6.5
root@b27e0e37a4b9:/vsts# pulumi version
v0.17.9

working:

root@544f76624d29:/pulumi# python3 --version
Python 3.6.7
root@544f76624d29:/pulumi# pulumi version
v0.17.4

could it be python version related?