This patch is basically just a big sed to update the variables:
s/PYTHON_LIBRARIES/Python3_LIBRARIES/g s/PYTHON_INCLUDE_DIRS/Python3_INCLUDE_DIRS/g s/PYTHON_EXECUTABLE/Python3_EXECUTABLE/g s/PYTHON_RPATH/Python3_RPATH/g
I've also renamed the CMake module to better express its purpose and for consistency with FindLuaAndSwig.