def clear_context(pid_file):
    """Called at exit. Delete the context file to signal there is no active notebook.

    We don't delete the whole file, but leave it around for debugging purposes. Maybe later we want to pass some information back to the web site.
    """
    return
    raise RuntimeError("Should not happen")
    fname = get_context_file_name(pid_file)
    shutil.move(fname, fname.replace("context.json", "context.old.json"))

    data = {}
    data["terminated"] = str(datetime.datetime.now(datetime.timezone.utc))
    set_context(pid_file, data)
Called at exit. Delete the context file to signal there is no active notebook.

    We don't delete the whole file, but leave it around for debugging purposes. Maybe later we want to pass some information back to the web site.