def METHOD_NAME(self):
    """
    1) Create an env file.
    2) Create a thread that creates a dict as one of env's elements, and
       keeps updating it, using the env save_lock attribute.
    3) Try to save the environment.
    """
    termination_event = threading.Event()
    env = utils_env.Env(filename=self.envfilename)
    def update_env(env):
        @utils_env.lock_safe
        def _update_env(env, key, value):
            env["changing_dict"][key] = value
        if "changing_dict" not in env:
            env["changing_dict"] = {}
        while True:
            key = "%s" % utils_misc.generate_random_string(length=10)
            value = "%s" % utils_misc.generate_random_string(length=10)
            _update_env(env, key, value)
            if termination_event.isSet():
                break
    changing_thread = threading.Thread(target=update_env,
                                       args=(env,))
    changing_thread.start()
    time.sleep(0.3)
    try:
        env.save()
    finally:
        termination_event.set()