Some format values are written as

"Scalar(0x..)"

The hotfix was to change the stripping rules, but this is probably
an incorrect implementation of certain traits for one of the curves.

halo2_frontend/src/dev/util.rs

@@ -63,7 +63,7 @@ pub(super) fn format_value<F: Field>(v: F) -> String {
         // Format value as hex.
         let s = format!("{v:?}");
         // Remove leading zeroes.
-        let s = s.strip_prefix("0x").unwrap();
+        let s = s.splitn(2, "0x").nth(1).unwrap().splitn(2, ")").nth(0).unwrap();
         let s = s.trim_start_matches('0');
         format!("0x{s}")
     }