Update op_pool to use proper rewards (#707)

* Update op_pool to use proper rewards

* Fix missing use import for tests

* Address Michael's comments

* Revert to private ValidatorStatuses

* Rename variable for clearer code

* Fix update_cover function

* Remove expect

* Add WIP test for rewards

* Use aggregation_bits instead of earliest_attestation_validators

* Use earliest attestation in test and correct typo

* Fix op_pool test thanks to @michaelsproul 's help

* Change test name

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -10,6 +10,7 @@ use crate::persisted_beacon_chain::{PersistedBeaconChain, BEACON_CHAIN_DB_KEY};
 use crate::timeout_rw_lock::TimeoutRwLock;
 use lmd_ghost::LmdGhost;
 use operation_pool::{OperationPool, PersistedOperationPool};
+use parking_lot::RwLock;
 use slog::{debug, error, info, trace, warn, Logger};
 use slot_clock::SlotClock;
 use ssz::Encode;
@@ -1514,7 +1515,11 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                 graffiti,
                 proposer_slashings: proposer_slashings.into(),
                 attester_slashings: attester_slashings.into(),
-                attestations: self.op_pool.get_attestations(&state, &self.spec).into(),
+                attestations: self
+                    .op_pool
+                    .get_attestations(&state, &self.spec)
+                    .map_err(BlockProductionError::OpPoolError)?
+                    .into(),
                 deposits,
                 voluntary_exits: self.op_pool.get_voluntary_exits(&state, &self.spec).into(),
             },