Initial validator trait. (#14)

* Initial validator trait.

* Add missing docs warning.

* Fix formatting.

* Fix validator output and serialization.

* Get rid of redundant ValidationCode type.

substrate/validator/src/error.rs

@@ -0,0 +1,33 @@
+// Copyright 2017 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
+
+use serializer;
+
+error_chain! {
+	foreign_links {
+		Serialization(serializer::Error);
+	}
+	errors {
+		Timeout {
+			description("Validation task has timed-out."),
+			display("Validation timeout."),
+		}
+		InvalidCode(details: String) {
+			description("The code is invalid."),
+			display("invalid code: '{}'", details),
+		}
+	}
+}