> Changing return type based on argument *values* is still a bad idea in
> general.

However load() and loads() do this. ;)

> It also makes it hard to plug the API in to generic code that is designed
> to work with any dump/load based serialisation protocol.

For dumps() it will be simple -- `lambda x: json.dumps(x, encoding='utf-8')`. For loads() it will be even simpler -- loads() will accept both strings and bytes.

Note that dumps() with the encoding parameter will be more 2.x compatible than current implementation. This will help in writing compatible code.