[Pkg-rust-maintainers] Bug#986891: decbargo: can't find yanked crates.

[peter green]

Package: debcargo

Debcargo can't find yanked crates, even when the yanked version is explicitly requested
through the "REALVER" environment variable.

Some crate upstreams will yank all the existing versions after posting a security
or other important fix. Since Debian policies/practices during freezes (and for stable
releases) often requires backporting fixes rather than packaging new upstream versions,
this can be a problem.