Content Security Policy: The page’s settings blocked the loading of a resource at https://fonts.gstatic.com/s/droidsans/v6/s-BiyweUPV0v-yRb-cjciC3USBnSvpkopQaUR-2r7iU.ttf (“default-src”). Content Security Policy: The page’s settings blocked the loading of a resource at https://fonts.gstatic.com/s/droidsansmono/v7/ns-m2xQYezAtqh7ai59hJYW_AySPyikQrZReizgrnuw.ttf (“default-src”).
Yay for CSP, but still a problem (and should be reported upstream?). This is fallout from T278905: Reconsider which mailman3 version we're running.