Everything was working when I have python 3.6.5 loaded :
After updating to 3.6.7, the Open Python Session fails:
Go to Solution.
3.6.6 also works.
3.6.7 doesn't work.
3.6.8 doesn't work.
So the incompatibility was introduced in 3.6.7:
Thank you for bringing this to our attention. I will be making some further investigations by replicating the issue and, if necessary, I will create a corrective action request to work on it further.