[Catalog-sig] Add link to secure connection to the PyPI front page

["Martin v. Löwis"]

> Installing it is not really such a major task, once you have
> the paperwork done. Should we take this to the PSF board for
> discussion ?

Essentially, I don't want to deal with that CA bureaucracy at all.
If you think that by taking it to the PSF board, you get all the
issues resolved, please go ahead. Installing it in the end is
indeed easy.

Regards,
Martin