KeyValueDB trait uses errors instead of strings

util/error/src/lib.rs

@@ -25,6 +25,7 @@ extern crate error_chain;
 extern crate ethcore_bigint as bigint;
 extern crate rlp;
 extern crate rustc_hex;
+extern crate kvdb;
 
 use std::fmt;
 use rustc_hex::FromHexError;
@@ -62,6 +63,10 @@ error_chain! {
 		UtilError, ErrorKind, ResultExt, Result;
 	}
 
+	links {
+		Db(kvdb::Error, kvdb::ErrorKind);
+	}
+
 	foreign_links {
 		Io(::std::io::Error);
 		FromHex(FromHexError);