Tests are failing on systems with python3, but without the python #129
Description
Describe the bug
Tests are failing because python isn't found.
How to reproduce
Run tests as in the docs without python tool.
Expected behavior
On many systems, often only the python3 is installed, and there isn't a symbolic link or a tool python. I suggest, we try finding python via different cmake helpers (like this: https://cmake.org/cmake/help/latest/module/FindPython.html ), and print an error message if python isn't found and some env shall be setup by the user. I understand, that on systems where we have zephyr, python is part of the .venv with west, so it shouldn't be a problem, but it's still possible to use ocre on linux systems where only python3 is installed.
Error message
