venv: pth files don't end up in site-packages

[rickeylev]

(I need to verify this, but I'm pretty sure this is true)

Packages with .pth files don't have them dropped into the site-packages root when venv_site_packages=yes is enabled. This prevents packages from installing their startup hooks.

If this is working (pretty sure it isn't), we should at least add a test for this. I'm very sure we don't have a test for it.

[aignas]

All of the data files should end up in the venv packages (i.e. we have #2936 that added that), so I would have thought it is working.

EDIT: checked by adding the rerun-sdk package and you are correct - the pth file does not get included.

[aignas]

I think I found the issue and added a test for this, PTAL.