old_contents: GnomePackage ('gtk-doc', version_major = '1', version_minor = '17', sources = [
          'http://ftp.gnome.org/pub/gnome/sources/%{name}/%{version}/%{name}-%{version}.tar.bz2'
  	])
  
new_contents: GnomePackage ('gtk-doc', version_major = '1', version_minor = '17', configure_flags = ['--with-xml-catalog="%{prefix}/etc/xml/catalog"'], sources = [
          'http://ftp.gnome.org/pub/gnome/sources/%{name}/%{version}/%{name}-%{version}.tar.bz2'
  	])
  
subject: Set xml catalog to the right prefix.