Switch to YAML::XS to work around insanity in YAML::Mo. Closes: #657533 https://rt.cpan.org/Ticket/Display.html?id=74487 Gave up trying to support multiple YAML backends. The XS one requires ugly manual encoding to get unicode right, and doesn't allow dumping yaml fragments w/o the yaml header, but at least it doesn't randomly crash on import like YAML::Mo has started to.