Marge fixes to test_harness, add serdehex crate

eth2/utils/bls/src/aggregate_signature.rs

@@ -2,7 +2,9 @@ use super::{AggregatePublicKey, Signature};
 use bls_aggregates::{
     AggregatePublicKey as RawAggregatePublicKey, AggregateSignature as RawAggregateSignature,
 };
+use serde::de::{Deserialize, Deserializer};
 use serde::ser::{Serialize, Serializer};
+use serde_hex::{encode as hex_encode, PrefixedHexVisitor};
 use ssz::{
     decode_ssz_list, hash, ssz_encode, Decodable, DecodeError, Encodable, SszStream, TreeHash,
 };
@@ -82,7 +84,19 @@ impl Serialize for AggregateSignature {
     where
         S: Serializer,
     {
-        serializer.serialize_bytes(&ssz_encode(self))
+        serializer.serialize_str(&hex_encode(ssz_encode(self)))
+    }
+}
+
+impl<'de> Deserialize<'de> for AggregateSignature {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let bytes = deserializer.deserialize_str(PrefixedHexVisitor)?;
+        let (obj, _) = <_>::ssz_decode(&bytes[..], 0)
+            .map_err(|e| serde::de::Error::custom(format!("invalid ssz ({:?})", e)))?;
+        Ok(obj)
     }
 }