Fix RPC error code conflict (#14315)

* Base error code module

* Base error code module

* fmt

substrate/client/rpc-api/src/error.rs

@@ -0,0 +1,28 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program 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.
+
+// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
+
+/// Base error code for RPC modules.
+pub mod base {
+	pub const AUTHOR: i32 = 1000;
+	pub const SYSTEM: i32 = 2000;
+	pub const CHAIN: i32 = 3000;
+	pub const STATE: i32 = 4000;
+	pub const OFFCHAIN: i32 = 5000;
+	pub const DEV: i32 = 6000;
+	pub const STATEMENT: i32 = 7000;
+}