Code review comment for lp://staging/~azzar1/unity/lockscreen

587 +void Controller::LockScreenUsingDisplayManager()
588 +{
589 + // TODO (andy) Move to a different class (DisplayManagerWrapper)
590 + const char* session_path_raw = g_getenv("XDG_SESSION_PATH");
591 + std::string session_path = session_path_raw ? session_path_raw : "";

You should just give up if $XDG_SESSION_PATH is undefined - you can't call Lock() without it.