Errands before 46.2.10 does not verify TLS certificates for CalDAV servers.
https://github.com/mrvladus/Errands/releases/tag/46.2.10
https://github.com/mrvladus/Errands/issues/401
https://github.com/mrvladus/Errands/compare/46.2.9...46.2.10
https://github.com/mrvladus/Errands/commit/04e567b432083fc798ea2249363ea6c83ff01099