use pex get_platform() method over distutils

src/python/pants/backend/python/tasks/setup_py.py

@@ -6,14 +6,14 @@
                         unicode_literals, with_statement)
 
 import ast
-import distutils.util
 import itertools
 import os
 import pprint
 import shutil
 from abc import abstractmethod
 from collections import OrderedDict, defaultdict
 
+import pex.pep425tags
 from pex.compatibility import string, to_bytes
 from pex.installer import InstallerBase, Packager
 from pex.interpreter import PythonInterpreter
@@ -61,7 +61,7 @@ class SetupPyRunner(InstallerBase):
 
   @classproperty
   def _local_platform_tag(cls):
-    return distutils.util.get_platform().replace('-', '_').replace('.', '_')
+    return pex.pep425tags.get_platform().replace('-', '_').replace('.', '_')
 
   # NB: "snapshot" refers to a "snapshot release", not a Snapshot.
   @classmethod