setup.py: except ImportError for missing pkg_resources

Missing pkg_resources indicates setuptools 82 or newer which is more recent that than 18.5 so the version check using pkg_resources can safely be skipped.

Author: loqs

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:
+    import pkg_resources
+    from pkg_resources import parse_version
+except ImportError:
+    pkg_resources = None
 
 try:
     import _markerlib.markers