Add py38 package metadata

Change-Id: I5f1182c2d33d2c28ce707713659e48e9afc463eb
diff --git a/setup.cfg b/setup.cfg
index 9da84c3..ebb8f8c 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -17,6 +17,7 @@
     Programming Language :: Python :: 3.5
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
 
 [files]
 packages =