Apply suggestions from code review

Co-authored-by: Jean-Philippe Raynaud <jp.raynaud@gmail.com>

Author: curiecrypt

mithril-stm/src/aggregate_signature/mod.rs

@@ -268,10 +268,10 @@ mod tests {
                         assert!(n < &params.k && k == &params.k)
                     },
                     Some(AggregationError::UnsupportedProofSystem(aggregate_signature_type)) => {
-                        println!("Unsupported proof system: {:?}", aggregate_signature_type);
+                        panic!("Unsupported proof system: {:?}", aggregate_signature_type);
                     },
                     _ => {
-                        println!("Unexpected error during aggregation: {:?}", error);
+                        panic!("Unexpected error during aggregation: {:?}", error);
                     }
                 },
             }

mithril-stm/src/aggregate_signature/signature.rs

@@ -1,8 +1,8 @@
-use anyhow::anyhow;
 use std::collections::HashMap;
 use std::fmt::Display;
 use std::hash::Hash;
 
+use anyhow::anyhow;
 use blake2::digest::{Digest, FixedOutput};
 use serde::{Deserialize, Serialize};
 
@@ -147,7 +147,7 @@ impl<D: Clone + Digest + FixedOutput + Send + Sync> AggregateSignature<D> {
                     )),
                 }
             })
-            .map_err(|_| anyhow!(AggregateSignatureError::BatchInvalid))
+
     }
 
     /// Convert an aggregate signature to bytes