[C++] Clean linkage of the python parser unit test

unittest/CMakeLists.txt

@@ -82,14 +82,12 @@ IF(LUA5_1_FOUND)
   ADD_TEST_CFLAGS(lua '-DPINOCCHIO_SOURCE_DIR=\\\"${${PROJECT_NAME}_SOURCE_DIR}\\\"')
 ENDIF(LUA5_1_FOUND)
 
-IF(${BUILD_PYTHON_INTERFACE} STREQUAL "ON")
-  IF(EIGENPY_FOUND)
-    ADD_UNIT_TEST(python_parser eigen3)
-    TARGET_LINK_LIBRARIES(python_parser ${Boost_LIBRARIES} ${PROJECT_NAME} ${PYTHON_LIBRARIES}
-      ${Boost_PYTHON_LIBRARIES})
-    ADD_TEST_CFLAGS(python_parser '-DPINOCCHIO_SOURCE_DIR=\\\"${${PROJECT_NAME}_SOURCE_DIR}\\\"')
-  ENDIF(EIGENPY_FOUND)
-ENDIF(${BUILD_PYTHON_INTERFACE} STREQUAL "ON")
+IF(BUILD_PYTHON_INTERFACE)
+  ADD_UNIT_TEST(python_parser eigen3)
+  TARGET_LINK_BOOST_PYTHON(python_parser)
+  TARGET_LINK_LIBRARIES(python_parser ${PYTHON_LIBRARIES})
+  ADD_TEST_CFLAGS(python_parser '-DPINOCCHIO_SOURCE_DIR=\\\"${${PROJECT_NAME}_SOURCE_DIR}\\\"')
+ENDIF(BUILD_PYTHON_INTERFACE)
 
 # Work in progress
 ADD_UNIT_TEST(constraint eigen3)