Fix Binary on python < 2.7.4 (closes #10593811) Before the fix for http://bugs.python.org/issue10211 we can't pass a buffer object to BytesIO, so keep using StringIO in that case. And because StringIO is an old-style class, we can't use super().

bgcolor = '#000000'
stylesheets = ['%s/cubicweb.css' % datadir_url]
logo = '%s/logo.png' % datadir_url
lazy = lazystr('%(bgcolor)s')