Merge pull request ethereum#243 from OffchainLabs/export-memdb-errors

Export errNotFound from memorydb to use it in Nitro error checks

ethdb/memorydb/memorydb.go

@@ -32,9 +32,9 @@ var (
 	// invocation of a data access operation.
 	errMemorydbClosed = errors.New("database closed")
 
-	// errMemorydbNotFound is returned if a key is requested that is not found in
+	// ErrMemorydbNotFound is returned if a key is requested that is not found in
 	// the provided memory database.
-	errMemorydbNotFound = errors.New("not found")
+	ErrMemorydbNotFound = errors.New("not found")
 
 	// errSnapshotReleased is returned if callers want to retrieve data from a
 	// released snapshot.
@@ -98,7 +98,7 @@ func (db *Database) Get(key []byte) ([]byte, error) {
 	if entry, ok := db.db[string(key)]; ok {
 		return common.CopyBytes(entry), nil
 	}
-	return nil, errMemorydbNotFound
+	return nil, ErrMemorydbNotFound
 }
 
 // Put inserts the given value into the key-value store.
@@ -374,7 +374,7 @@ func (snap *snapshot) Get(key []byte) ([]byte, error) {
 	if entry, ok := snap.db[string(key)]; ok {
 		return common.CopyBytes(entry), nil
 	}
-	return nil, errMemorydbNotFound
+	return nil, ErrMemorydbNotFound
 }
 
 // Release releases associated resources. Release should always succeed and can