[CMake] add missing link with dynamic-graph-python

Fix build on Debian stretch.

unitTesting/CMakeLists.txt

@@ -45,6 +45,9 @@ FOREACH(test ${tests})
   PKG_CONFIG_USE_DEPENDENCY(${test} pinocchio)
   PKG_CONFIG_USE_DEPENDENCY(${test} sot-core)
   PKG_CONFIG_USE_DEPENDENCY(${test} dynamic-graph)
+  IF(BUILD_PYTHON_INTERFACE)
+    TARGET_LINK_LIBRARIES(${test} dynamic-graph-python)
+  ENDIF(BUILD_PYTHON_INTERFACE)
 
   IF(${test}_plugins_dependencies)
     ADD_DEPENDENCIES(${EXECUTABLE_NAME} "${${test}_plugins_dependencies}")