使用CloudPathLib从公有AWS S3 Bucket下载文件夹遇凭证报错

我尝试使用Python库cloudpathlib从公有AWS S3 Bucket下载文件夹，代码如下：

from cloudpathlib import CloudPath
path = r"C:\some\path\to\folder"
url = "s3://some-example-bucket/folder/"

cloud_path = CloudPath(url)
cloud_path.download_to(path)

操作逻辑十分简单，按常理这个Bucket是公有的，代码应该能正常运行。

以下是Bucket策略（取自AWS S3教程）：

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "PublicRead",
            "Effect": "Allow",
            "Principal": "*",
            "Action": [
                "s3:GetObject",
                "s3:GetObjectVersion"
            ],
            "Resource": "arn:aws:s3:::cozy-auto-texture-sd-repo/*"
        }
    ]
}

但运行代码下载stable-diffusion-v1-4文件夹时，出现如下报错：

File "E:\Cozy-Auto-Texture-Files\venv\lib\site-packages\botocore\auth.py", line 418, in add_auth
    raise NoCredentialsError()
botocore.exceptions.NoCredentialsError: Unable to locate credentials

我的问题是：为何会出现这种情况？该Bucket是公有的，不应需要凭证。是Bucket权限配置存在遗漏，还是Python代码的问题？

补充说明：
我还尝试了使用boto3的方法：

BUCKET_NAME = 'cozy-auto-texture-sd-repo'  # replace with your bucket name
KEY = 'stable-diffusion-v1-4'

s3 = boto3.resource('s3')

try:
    s3.Bucket(BUCKET_NAME).download_file(KEY, sd_path)
except botocore.exceptions.ClientError as e:
    if e.response['Error']['Code'] == "404":
        print("The object does not exist.")
    else:
        raise

但仍出现相同的NoCredentialsError报错，因此我怀疑是S3 Bucket的配置存在问题。

内容的提问来源于stack exchange，提问作者Torrin worx