[dev] remove distutils from dependency (#6089)

dglgo/setup.py

 #!/usr/bin/env python
 
-from distutils.core import setup
-
-from setuptools import find_packages
+from setuptools import find_packages, setup
 
 setup(
     name="dglgo",

python/dgl/__init__.py

@@ -9,8 +9,6 @@ and transforming graphs.
 # This initializes Winsock and performs cleanup at termination as required
 import socket
 
-from distutils.version import LooseVersion
-
 # Backend and logging should be imported before other modules.
 from .logging import enable_verbose_logging  # usort: skip
 from .backend import backend_name, load_backend  # usort: skip

python/setup.py

@@ -2,21 +2,13 @@
 # -*- coding: utf-8 -*-
 import glob
 import os
-import platform
 import shutil
 import sys
 import sysconfig
 
-from setuptools import find_packages
+from setuptools import find_packages, setup
 from setuptools.dist import Distribution
-
-# need to use distutils.core for correct placement of cython dll
-if "--inplace" in sys.argv:
-    from distutils.core import setup
-    from distutils.extension import Extension
-else:
-    from setuptools import setup
-    from setuptools.extension import Extension
+from setuptools.extension import Extension
 
 
 class BinaryDistribution(Distribution):