Function render_warnings 

pub fn render_warnings(warnings: &[Warning<'_>]) -> String

What a caller should print for the deprecations a command line used.

The same arrangement as render_failure, and for the same reason: whether the coloured rendering is available is a feature of this crate in the adopter’s dependency graph, so the #[cfg] lives beside the thing it gates rather than in generated code.

Warnings are not failures. A caller prints these to stderr and carries on.