Make RoutingTableReaderError publicly available
This change makes the RoutingTableReaderError publicly available as it
is part of the reader trait, but does not share the same visibility.
@@ -39,7 +39,7 @@ pub mod memory;
use std::cmp::Ordering;
use std::fmt;
-use self::error::RoutingTableReaderError;
+pub use self::error::RoutingTableReaderError;
use crate::error::InternalError;
use crate::error::InvalidStateError;
