Added 3.8 explicitly in the metadata

Author: Sylvain MARIE

setup.py

@@ -82,7 +82,7 @@
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
-
+        'Programming Language :: Python :: 3.8',
         # 'Framework :: Pytest'
     ],