PROTON-2324 Support Python 3.9 (#320)

diff --git a/python/setup.py.in b/python/setup.py.in
index 1c77c30..a83d0d5 100644
--- a/python/setup.py.in
+++ b/python/setup.py.in
@@ -272,13 +272,12 @@
       classifiers=["License :: OSI Approved :: Apache Software License",
                    "Intended Audience :: Developers",
                    "Programming Language :: Python",
-                   "Programming Language :: Python :: 2",
-                   "Programming Language :: Python :: 2.7",
                    "Programming Language :: Python :: 3",
-                   "Programming Language :: Python :: 3.5",
+                   "Programming Language :: Python :: 3 :: Only",
                    "Programming Language :: Python :: 3.6",
                    "Programming Language :: Python :: 3.7",
-                   "Programming Language :: Python :: 3.8"],
+                   "Programming Language :: Python :: 3.8",
+                   "Programming Language :: Python :: 3.9"],
       cmdclass={
           'configure': Configure,
           'swig': Swig,