Fix datetime deprecation warning

[bubai2000]

When running boto3 on Python 3.12 environment, there is a deprecation warning "DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC)". This PR tries to address this issue.

[kurtmckee]

I've already opened a PR to address this: #3239.

The method used in this PR has been previously attempted, but had to be discarded because it made the datetime objects timezone-aware.

In addition, the datetime.UTC alias used in this PR is only available in Python 3.11 and higher, and would cause AttributeErrors in lower Python versions.

[bubai2000]

Understandable. Can you please share a solution for this?

[kurtmckee]

PR #3239 is the solution. Unfortunately, the maintainers of botocore have not reviewed and merged the PR yet.

You can suppress the warnings by configuring Python and/or pytest warnings. I recommend searching for "python suppress warnings" and "pytest suppress warnings", depending on your needs.

[bubai2000]

Thanks a lot!