Fixes #868 -- test on py38 (#870)

diff --git a/setup.py b/setup.py
index ec66539..f6d5499 100755
--- a/setup.py
+++ b/setup.py
@@ -81,6 +81,7 @@
             'Programming Language :: Python :: 3.5',
             'Programming Language :: Python :: 3.6',
             'Programming Language :: Python :: 3.7',
+            'Programming Language :: Python :: 3.8',
 
             'Programming Language :: Python :: Implementation :: CPython',
             'Programming Language :: Python :: Implementation :: PyPy',