Fix broken build on readthedocs, second attempt

Author: stefano-maggiolo

docs/conf.py

@@ -28,7 +28,7 @@ class Mock(MagicMock):
     def __getattr__(cls, name):
             return Mock()
 
-MOCK_MODULES = ['cups']
+MOCK_MODULES = ['pycups']
 sys.modules.update((mod_name, Mock()) for mod_name in MOCK_MODULES)