> By the way, I'm surprised that the special encoding "unicode" relies on the *current* locale encoding when the XML declaration is requested. Why not alway susing UTF-8 for *unicode* instead of the locale encoding?

Because it is usually outputs to sys.stdout or a file opened with default encoding. Agreed, the current locale encoding is not the best choice. It would be better to look at the encoding attribute of the file and fallback to utf-8 or ascii.