As setuptools is not the build backend there should be no reliance on setuptools or distutils for use. This exchanges the deprecated distutils.dir_util.copy_tree for shutil.copytree as recast-atlas is Python 3.8+.
Note that as distutils is also deprecated, if this was not done then setuptools._distutils.dir_util.copy_tree would need to be used.
distutils.dir_util.copy_treeforshutil.copytreeasrecast-atlasis Python 3.8+.