Since Failure is now deprecated, and Rust's own std::error::Error trait
doesn't preserve a backtrace on Stable, if we want to move to a
supported library the most obvious successor is Anyhow.
The #[macro_export(local_inner_macros)] attribute is intended for macros
that require compatibility with rustc <1.30. When targeting only
compilers that support calling macros as $crate::m!(...), that should be
used instead.