While the update to apt-listbugs 0.1.42 does indeed trigger the reported problem, its cause is not in apt-listbugs code itself.
This update uses https by default, but one of the servers answering to bugs.debian.org (bembo.debian.org) uses a TLS certificate that is not signed by a well-known authority, leading to the certificate verification failure. The other server answering to bugs.debian.org (buxtehude.debian.org) does not have this problem, so people might not get this certificate error when using apt-listbugs if they are lucky enough to contact the server with the correct TLS configuration. What should be fixed here is the TLS certificate served by bembo.debian.org, not apt-listbugs itself.
