There seems to be a very minor bug in the ElementTree.py file, for the so-called 'empty' elements that are serialized without a closing tag. The HTML_EMPTY tuple/set is used to lookup these tags.

In the Lib/xml/etree/ElementTree.py file, the HTML_EMPTY tuple is created like:

HTML_EMPTY = ("area", "base", "basefont", "br", "col", "frame", "hr",
              "img", "input", "isindex", "link", "meta" "param")

There is a missing comma between "meta" and "param". I'm not sure if this is intended behavior.

The line should be replaced with:

HTML_EMPTY = ("area", "base", "basefont", "br", "col", "frame", "hr",
              "img", "input", "isindex", "link", "meta", "param")