The bug tracker, https://bugs.g10code.com/, uses a certificated signed by the
CACert class 3 CA. That CA certificate is itself signed by the CACert class 1
CA. Therefore, in addition to its own server certificate, the server is
supposed to send the class 3 CA as part of the TLS handshake (this would be
configured in Apache, for example, using the SSLCertificateChainFile
directive). This will cause the site to validate properly in browsers that only
have class 1 CA installed. However, it does not send this certificate in its
handshake.