Add missing comma (#76)

Author: emlaver

setup.py

@@ -82,7 +82,7 @@ def finalize_options(self):
           'Programming Language :: Python :: 3.6',
           'Programming Language :: Python :: 3.7',
           'Programming Language :: Python :: 3.8',
-          'Programming Language :: Python :: 3.9'
+          'Programming Language :: Python :: 3.9',
           'Development Status :: 4 - Beta',
           'Intended Audience :: Developers',
           'License :: OSI Approved :: Apache Software License',