CMake 3.12 requirement

[pdimov]

CMake 3.12 is required here

histogram/CMakeLists.txt

Line 6 in 3afe76f

cmake_minimum_required(VERSION 3.12...3.27)

but I'm not sure why; from a quick look at the CML files nothing seems to need it.

Ubuntu 18.04 has CMake 3.10, and we're adding CI jobs to test with earlier CMake versions, so this came up.

[HDembinski]

I am not sure either, I probably copy/pasted that from some source. We can try to lower it to 3.10 and test it.

[henryiii]

cda7447

Needed for FindPackage Python. But I’m assuming that is only for tests or something that is not always required?

3.10 is really old, btw. ;)