Fixed error in setup.py

Author: rohe

setup.py

@@ -42,7 +42,7 @@
         "License :: OSI Approved :: Apache Software License",
         "Topic :: Software Development :: Libraries :: Python Modules",
         "Programming Language :: Python :: 3.5",
-        "Programming Language :: Python :: 3.6"
+        "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7"
     ],
     install_requires=["cryptography", "requests"],