Add webob to test_requires for python3

Code paths seem different which ends up leading to webob needing to be
present.

Author: SpamapS

setup.py

@@ -42,6 +42,7 @@ def run_tests(self):
     'python-memcached >= 1.51',
     'pytest',
     'mako',
+    'webob',
     #'pytest-coverage',
 ]