https://github.com/brianmcd/contextify/blob/master/README.md says:
> As of Node 0.12, Contextify has been merged into Node (thanks to @domenic), > replacing the native vm module. The code has been improved on since then, so > if at all possible, you should use a newer Node and the native vm module. This package is no longer required and should removed from Debian. -- Edward.