Out of curiosity, why are you borrowing that many times? The following should work:

    while let Some(page) = object_stream.next().await {
        match page {
            // ListObjectsV2Output
            Ok(p) => {
                if let Some(contents) = p.contents {
                    all_objects.extend(contents);
                }
            }
            // SdkError<ListObjectsV2Error, Response>
            Err(err) => {
                let raw_response = err.raw_response();
                let service_error = err.as_service_error();
                error!("ListObjectsV2Error: {:?} {:?}", service_error, raw_response);
                return Err(S3Error::Error(format!("ListObjectsV2Error: {:?}", err)));
            }
        }
    }

I would have written it this way

    while let Some(page) = object_stream.next().await {
        let p: ListObjectsV2Output = page.map_err(|err| {
            // SdkError<ListObjectsV2Error, Response>
            let raw_response = err.raw_response();
            let service_error = err.as_service_error();
            error!("ListObjectsV2Error: {service_error:?} {raw_response:?}");
            S3Error::Error(format!("ListObjectsV2Error: {err:?}"))
        })?;
        if let Some(contents) = p.contents {
            all_objects.extend(contents);
        }
    }

although if your crate defines `S3Error`, then I would prefer to write

    while let Some(page) = object_stream.next().await {
        if let Some(contents) = page?.contents {
            all_objects.extend(contents);
        }
    }

by implementing `From`:

    impl From<SdkError<ListObjectsV2Error, Response>> for S3Error {
        fn from(err: SdkError<ListObjectsV2Error, Response>) -> S3Error {
            let raw_response = err.raw_response();
            let service_error = err.as_service_error();
            error!("ListObjectsV2Error: {service_error:?} {raw_response:?}");
            S3Error::Error(format!("ListObjectsV2Error: {err:?}"))
        }
    }