Website verification only via HTTP even though I have CA installed locally

My website’s certificate is issued by [CAcert](http://www.cacert.org), a Web of Trust-based CA that’s not in most CA collections. When checking my proof (`keybase id lucaswerkmeister`), the client only does the verification over HTTP, even though I have the CAcert certificates installed on my system (e. g., `curl https://lucaswerkmeister.de/keybase.txt` works fine). It would be better if the client made that connection via HTTPS, at least on systems that have the certificate.

Start by reproducing the issue with `keybase id lucaswerkmeister` and compare its HTTP verification with `curl https://lucaswerkmeister.de/keybase.txt`, which succeeds using the locally installed CAcert certificates. Trace the client’s website-proof verification path; done means HTTPS verification works when the system trusts the certificate, while existing verification remains functional otherwise.

Written by the indexing model from the issue text.