util: disinfect lookup_reg strings (issue1126)
lookup_reg could return Unicode strings, which would infect other strings and
generate unexpected tracebacks. Spotted by Rémy Roy.
Fold in silly nested function while we're at it.
<?xml version="1.0" encoding="{encoding}"?>
<rss version="2.0">
<channel>
<link>{urlbase}{url}</link>
<language>en-us</language>