FindPython3 doesn't work under conda-build since CMake 3.17.0
This is a regression in CMake 3.17.0, it used to work in 3.16.*: https://dev.azure.com/ursa-labs/crossbow/_build/results?buildId=9143&view=logs&j=0da5d1d9-276d-5173-c4c4-9d4d4ed14fdb&t=d9b15392-e4ce-5e4c-0c8c-b69645229181&l=695
In this build, it should have found the Python 3.6 interpreter installed in the build environment.
Edited by Brad King