SW-382: simplified CMakeLists.txt for PyMessaging

LCS/Messaging/python/CMakeLists.txt

 # $Id: CMakeLists.txt 1584 2015-10-02 12:10:14Z loose $
 
-lofar_find_package(Python 3.4)
-if(PYTHON_FOUND)
-  lofar_add_package(PyMessaging messaging)
-else()
-  message(WARNING "Python module lofar.messaging will NOT be built")
-endif()
+lofar_add_package(PyMessaging messaging)

LCS/Messaging/python/messaging/CMakeLists.txt

@@ -2,6 +2,11 @@
 
 lofar_package(PyMessaging 1.0 DEPENDS PyCommon)
 
+lofar_find_package(Python 3.4 REQUIRED)
+
+include(FindPythonModule)
+find_python_module(proton)
+
 include(PythonInstall)
 
 set(_py_files