[31m[1mERROR[0m[39m: 
  [31m×[0m Error observers must take a reference to Pavex's common error type as
  [31m│[0m input (`&pavex::Error`).
  [31m│[0m `app::error_observer` doesn't.
  [31m│[0m
  [31m│[0m     ╭─[[36;1;4msrc/lib.rs[0m:9:1]
  [31m│[0m  [2m 9[0m │     let mut bp = Blueprint::new();
  [31m│[0m  [2m10[0m │     bp.error_observer(f!(crate::error_observer));
  [31m│[0m     · [35;1m                      ────────────┬────────────[0m
  [31m│[0m     ·                   [35;1mThe error observer was registered here[0m
  [31m│[0m  [2m11[0m │     bp
  [31m│[0m     ╰────