s3.upload_object_via_stream no longer accepts an iterator with unknown length

With libcloud 2.0.0, it's no longer possible to send an iterator of unknown length to upload_object_via_stream. (Using it with GoogleStorageDriver myself.)

My use case is using iter(data) instead of io.BytesIO(data) + having to import io. In other words, I can work around the issue, but there are probably valid use cases for this.

Is the new behavior intended, or is it a bug that should be fixed?