出现此错误的原因可能是因为您未获得使用设备影子REST API的权限。请确保已为您的AWS账户授予所需的权限，并在请求时提供所需的权限令牌。

以下是一些示例代码，可用于将权限令牌添加到您的AWS设备影子REST API请求中：

import boto3
from botocore.exceptions import ClientError

# 创建IAM访问密钥
access_key = 'your-access-key'
secret_key = 'your-secret-key'

# 创建IAM角色和STS令牌
iam = boto3.client('iam', aws_access_key_id=access_key,
                   aws_secret_access_key=secret_key,
                   region_name='us-east-1')
sts = boto3.client('sts', aws_access_key_id=access_key,
                   aws_secret_access_key=secret_key,
                   region_name='us-east-1')

assume_role_response = sts.assume_role(
    RoleArn='arn:aws:iam::160501803049:role/my-iot-role',
    RoleSessionName='my-iot-session'
)

# 使用角色STS令牌创建AWS设备影子REST API客户端
client = boto3.client('iot-data', aws_access_key_id=access_key,
                      aws_secret_access_key=secret_key,
                      aws_session_token=assume_role_response['Credentials']['SessionToken'],
                      region_name='us-east-1')

# 调用设备影子REST API请求
try:
    response = client.get_thing_shadow(thingName='my-iot-thing')
    print(response['payload'].read())
except ClientError as e:
    print(e.response['Error']['Code'])