It looks like sitemap checking never worked, this is an attempt to fix that as well as Python 3 support. Having said that I haven't done a successful check of a real world sitemap file.

I have gone back to url_data.get_content(), i.e. passing a string to xmlparser.Parse() and it is succeeding here on Python 2. @mgedmin I don't know what test data you used that failed, maybe this works because the test file states an encoding? Else we could pass the encoding from url_data to xml.parsers.expat.ParserCreate() and force the issue.