The old code set the output-encoding to None, which means, I want
Unicode strings as output.  This made Mako pass markupsafe objects to
"unicode()", which applied all the escaping.  Then the result would be
given to Django, would would html-escape it again, resulting in
over-escaping.

By setting the output-encoding to utf8, we use filters.encode.utf8
instead, which is aware of Markupsafe, which avoids the over-escaping.