Due to po4a bug:
 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=518218
addendum is activated with the work around to handle <bookinfo> tag properly in
po4a/po4a.cfg as:

 opt:"-o nodefault=<bookinfo> -o break=<bookinfo> -o untranslated=<bookinfo>"

However, note that Bug#518218 was fixed in po4a 0.55-1 in Dec 2018.
