Manifest Hooks?

[Steven Stallion]

All,

I've been looking into using manifests to help track some project
dependencies and had a question for the list. Is it possible to add a
shell hook similar to nix-shell when the packages specified by a
manifest have been installed? In this specific case, I have a Python
virtualenv I would like to activate when packages have finished
installing without requiring additional scripting.

Thanks in advance!
Steve