Fix SSZ for bls fake_crypto features

eth2/utils/bls/src/fake_aggregate_signature.rs

@@ -3,7 +3,7 @@ use cached_tree_hash::cached_tree_hash_ssz_encoding_as_vector;
 use serde::de::{Deserialize, Deserializer};
 use serde::ser::{Serialize, Serializer};
 use serde_hex::{encode as hex_encode, PrefixedHexVisitor};
-use ssz::{ssz_encode, Decodable, DecodeError, Encodable};
+use ssz::{ssz_encode, Decodable, DecodeError};
 use tree_hash::tree_hash_ssz_encoding_as_vector;
 
 /// A BLS aggregate signature.
@@ -57,6 +57,24 @@ impl FakeAggregateSignature {
     ) -> bool {
         true
     }
+
+    /// Convert bytes to fake BLS aggregate signature
+    pub fn from_bytes(bytes: &[u8]) -> Result<Self, DecodeError> {
+        if bytes.len() != BLS_AGG_SIG_BYTE_SIZE {
+            Err(DecodeError::InvalidByteLength {
+                len: bytes.len(),
+                expected: BLS_AGG_SIG_BYTE_SIZE,
+            })
+        } else {
+            Ok(Self {
+                bytes: bytes.to_vec(),
+            })
+        }
+    }
+
+    pub fn as_bytes(&self) -> Vec<u8> {
+        self.bytes.clone()
+    }
 }
 
 impl_ssz!(