Version 5.0.0-3 of rust-onig is marked for autoremoval from testing on Tue 10 Nov 2020. It is affected by #971141. The removal of rust-onig will also cause the removal of (transitive) reverse dependencies: rust-bat, rust-syntect. It depends (transitively) on rust-onig-sys, affected by #971147. You should try to prevent the removal by fixing these RC bugs.
vcswatch reports that
this package seems to have a new changelog entry (version
UNRELEASED-FIXME-AUTOGENERATED-DEBCARGO) and new commits
in its VCS. You should consider whether it's time to make