I recently came across this: https://github.com/spotify/dh-virtualenv

For a system utility, you can still use virtualenvs. The launcher script just needs to use a shebang like:

    #!/usr/share/spiffyapp/venv/bin/python

My rule of thumb is to never install anything into system Python by pip, etc. If it's not an OS package, it belongs to a virtualenv.

I more or less have this rule, except I generally will use the --user flag to install things on a per-user basis if it's not being installed for a particular project.