Yes, that. I look regularly at https://qa.debian.org/dose/debcheck/src_testing_main/ as we (the release team) require packages to be buildable in testing (we have some tolerance as the migration of build dependencies isn't guaranteed when checking if a package may migrate). Please help the rust maintainers such that that package can migrate.
rust-xdg (for which a fix was just uploaded) isn't the only build-dependency of newsboat that is not currently in testing.
rust-curl-sys is also failing to migrate, the autopkgtest is failing to start due to a debcargo issue. Furthermore looking back at test history it seems that there are (or at least were) other test issues once the autopkgtest runs. See bug 958547 (which was incorrectly closed by the maintainer) for further details.