The package which provides the RPM macros for Rust packaging was renamed from rust-packaging to cargo-rpm-macros as part of a big rewrite. The Guidelines need to be updated, since they currently state that packages need to have BuildRequires: rust-packaging, which is no longer true.

They either need BuildRequires: rust-packaging >= 21 (if the project in question does not use functionality that was only implemented with the cargo-rpm-macros rewrite) or BuildRequires: cargo-rpm-macros >= 24 (if the project's metadata uses specific syntax which is not supported by the old rust-packaging).

PS: The rust2rpm tool now generates these BuildRequires as required (i.e. it only includes BuildRequires: cargo-rpm-macros >= 24 if the crate uses the new features, but includes BuildRequires: rust-packaging >= 21 if the crate is still compatible with the old packaging tools (which are still present on EPEL9, for example). This ensures backwards compatibility (where possible).