The problem is on cPanel version is out of date, it’s still trying to detect file search.cpan.org which doesn't exist.

This case you'll need to update cpan in your server by this guide:
http://perltricks.com/article/44/2013/10/20/Find-CPAN-mirrors-and-configure-the-local-CPAN-mirror-list

Edit file
/root/.cpan/CPAN/MyConfig.pm
Or
/usr/share/perl5/CPAN/Config.pm

Change urllist

to be
'urllist' => [
    q[http://httpupdate3.cpanel.net/CPAN/],
    q[http://httpupdate23.cpanel.net/CPAN/],
   q[http://mirrors.servercentral.net/CPAN/],
    q[ftp://cpan.cse.msu.edu/]
],

After that, install RVsitebuilder (V6) again.