Seco::Multipkg::CPAN doesn't properly handle incorrect permissions on the .cpan directory

[cuzelac]

If permissions on your ~/.cpan directory are incorrect, Seco::Multipkg::CPAN holds with no errors to STDOUT/STDERR.

I had to strace to figure out what was going on:

write(1, "WARNING: CPAN.pm is unable to write a configuration file. You\nmust be able to create and write to '/home/vagrant/.cpan/CPAN/MyConfig.pm'.\n\nAborting configuration.\n", 164) = 164

/home/vagrant/.cpan/CPAN/MyConfig.pm was owned by root and multipkg was running as user 'vagrant'

We should either use a temp .cpan directory or do proper perms checking on the default.