setup.py: handle missing pkg_resources import

Signed-off-by: Rui Chen <rui@chenrui.dev>

Author: chenrui333

setup.py

@@ -6,9 +6,12 @@
 
 from os.path import join, dirname
 from setuptools import setup, find_packages, __version__ as setuptools_version
-from pkg_resources import parse_version
-
-import pkg_resources
+try:
+    from pkg_resources import parse_version
+    import pkg_resources
+except ModuleNotFoundError:
+    from setuptools._vendor.packaging.version import parse as parse_version
+    pkg_resources = None
 
 try:
     import _markerlib.markers