[Cleanup] storage/s3-sdk: Adds docstrings, return value instead of print

[askmeegs]

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.9 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[dandhlee]

Are there any reason to switch to returning a list rather than printing them?

[engelke]

Are there any reason to switch to returning a list rather than printing them?

Yes. We want to test against returned values rather than captured strings.

[engelke]

Please remove "capsys" parameters and fix lint's nitpicking. You don't need to wait for another review from me. LGTM.

[tritone]

Are there any reason to switch to returning a list rather than printing them?

Yes. We want to test against returned values rather than captured strings.

Have we changed that in general across samples? I see this in the standards still: https://googlecloudplatform.github.io/samples-style-guide/#result

[engelke]

Are there any reason to switch to returning a list rather than printing them?

Yes. We want to test against returned values rather than captured strings.

Have we changed that in general across samples? I see this in the standards still: https://googlecloudplatform.github.io/samples-style-guide/#result

The instructions for FixIt don't require removing printing, just no longer basing tests on that instead of on returned values.