Improve cassandra_connection panic message (#663)

shotover-proxy/tests/helpers/cassandra.rs

@@ -10,7 +10,9 @@ pub fn cassandra_connection(contact_points: &str, port: u16) -> Session {
  cluster.set_credentials("cassandra", "cassandra").unwrap();
  cluster.set_port(port).ok();
  cluster.set_load_balance_round_robin();
- cluster.connect().unwrap()
+ // By default unwrap uses the Debug formatter `{:?}` which is extremely noisy for the error type returned by `connect()`.
+ // So we instead force the Display formatter `{}` on the error.
+ cluster.connect().map_err(|err| format!("{err}")).unwrap()
 }
 
 #[derive(Debug, Clone, PartialOrd, PartialEq, Eq, Ord)]