Macro abortable_parser::with_err

macro_rules! with_err {
    ($i:expr, $f:ident!( $( $args:tt )* ), $e:expr) => { ... };
    ($i:expr, $f:ident( $( $args:tt )* ), $e:expr ) => { ... };
    ($i:expr, $f:ident, $e:expr) => { ... };
}

Replaces the the sub error in a Fail case with one of your own errors.