Error on the new update 5.0.0

[ABODFTW]

Problem description

I had a code snippet on my code base that used smart_open to upload a file to S3 Bucket, but suddenly after I reinitiated the venv, it started failing and is giving me this error:
CreateMultipartUpload operation: The AWS Access Key Id you provided does not exist in our records.'))
Though the Access Key ID is correct, and after a couple of hours of debugging, I found that the only thing that changed is smart_open version, and after downgrading to 4.2.0 it just worked with the same credentials.

session = boto3.Session(
        aws_access_key_id=settings.AWS_ACCESS_KEY_ID,
        aws_secret_access_key=settings.AWS_SECRET_ACCESS_KEY,
        region_name=settings.AWS_S3_REGION_NAME,
    )
bucket = settings.AWS_STORAGE_BUCKET_NAME
endpoint_url = settings.AWS_S3_ENDPOINT_URL
filename = uuid.uuid4().hex
path = f"{bucket}/outputs/{filename}.csv"
with smart_open.open(
    f"s3://{path}",
    "w",
    transport_params={
        "session": session,
        "multipart_upload_kwargs": {"ACL": "public-read"},
        "resource_kwargs": {
            "endpoint_url": endpoint_url,
        },
    },
) as f:
    df.to_csv(f)

Versions

Please provide the output of:

Working version:

>>> import platform, sys, smart_open
>>> print(platform.platform())
Linux-5.4.72-microsoft-standard-WSL2-x86_64-with-glibc2.29
>>> print("Python", sys.version)
Python 3.8.5 (default, Jan 27 2021, 15:41:15)
[GCC 9.3.0]
>>> print("smart_open", smart_open.__version__)
smart_open 4.2.0

Probolmatic version:

>>> import platform, sys, smart_open
>>> print(platform.platform())
Linux-5.4.72-microsoft-standard-WSL2-x86_64-with-glibc2.29
>>> print("Python", sys.version)
Python 3.8.5 (default, Jan 27 2021, 15:41:15)
[GCC 9.3.0]
>>> print("smart_open", smart_open.__version__)
smart_open 5.0.0
>>>

Checklist

Before you create the issue, please make sure you have:

• Described the problem clearly
• Provided a minimal reproducible example, including any required data
• Provided the version numbers of the relevant software

[mpenkov]

Please see https://github.com/RaRe-Technologies/smart_open/blob/develop/MIGRATING_FROM_OLDER_VERSIONS.rst#migrating-to-the-new-client-based-s3-api

[piskvorky]

@mpenkov any way we can catch the "old" use, and issue a warning?

Because this seems to come up a lot, tripping up users.

[ABODFTW]

Thanks for the info @mpenkov, and as @piskvorky said, it would be optimal if there was some type of warning.

Even adding a small note on the repo readme denoting that there is some changes to the new version, and then linking to the link @mpenkov mentiond would help.

Thank you guys for the awesome work, it's such a pleasure using this tool.