VO variables logic

[Lewih]

How should variables like $VSC_DATA_VO should be handled?

Test should have logic to ensure it is set (correctly) when it should be set (like UGent VSC account in non-default VO)
User based env test according to the site where the user is logged in

$VSC_DATA_VO should always be set to /does/not/exist for sites that don't use VO concept
having it set to an incorrect value is better than not defining it (think use of $VSC_DATA_VO in job scripts that are shared across sites)