> Tools like svn and hg have extensive configurations for this purpose, and
> (at least hg) secure defaults; I certainly remember having to deal with hg
> complaining about the security of some repo site, where the fix was
> something I had to put in my .hgrc. That's interactive enough.

It is not about svn and hg, it was just an example that even in the
python.org realm we have used certificates that were (deliberately, in a
way) untrusted by major software.