adding a python node that uses opencv - ROS Indigo

edit

I followed this guide http://rodrigoberriel.com/2014/10/ins... for setting up OpenCV for ROS Indigo (since it doesn't come bundled anymore).

Now, the problem is I don't have an executable node that is produced from a CPP source file for target_link_libraries but I have a python node that uses OpenCV.

After adding 1)

all the dependencies in "package.xml" file,

and 2)

find_package(OpenCV REQUIRED)
include_directories(${OpenCV_INCLUDE_DIRS})
target_link_libraries(${OpenCV_LIBS})

in the CMakeLists.txt file, I get this error:

CMake Error at HELLO_WORLD/CMakeLists.txt:168 (target_link_libraries):
  Cannot specify link libraries for target "HELLO_WORLD" which is not built
  by this project.

How do I resolve this issue? Other nodes written in Python, I can just say "rosrun [PACKAGE_NAME] python_node.py" But in this Python node that uses OpenCV, I need to make changes appropriately in the CMakeLists.txt file. Only, I'm not quite sure what it is. sources I've referred to talk about CPP nodes.