rpc: change no wallet loaded message to be clearer

Changes the no wallet is loaded rpc error message to be clearer that no
wallet is loaded and how the user can load or create a wallet. Also
changes the error code from METHOD_NOT_FOUND to RPC_WALLET_NOT_FOUND as
that makes more sense.

Author: achow101

src/wallet/rpcwallet.cpp

@@ -112,7 +112,7 @@ std::shared_ptr<CWallet> GetWalletForJSONRPCRequest(const JSONRPCRequest& reques
 
     if (wallets.empty()) {
         throw JSONRPCError(
-            RPC_METHOD_NOT_FOUND, "Method not found (wallet method is disabled because no wallet is loaded)");
+            RPC_WALLET_NOT_FOUND, "No wallet is loaded. Load a wallet using loadwallet or create a new one with createwallet. (Note: A default wallet is no longer automatically created)");
     }
     throw JSONRPCError(RPC_WALLET_NOT_SPECIFIED,
         "Wallet file not specified (must request wallet RPC through /wallet/<filename> uri-path).");

test/functional/wallet_multiwallet.py

@@ -204,7 +204,7 @@ def wallet_file(name):
 
         self.restart_node(0, ['-nowallet'])
         assert_equal(node.listwallets(), [])
-        assert_raises_rpc_error(-32601, "Method not found", node.getwalletinfo)
+        assert_raises_rpc_error(-18, "No wallet is loaded. Load a wallet using loadwallet or create a new one with createwallet. (Note: A default wallet is no longer automatically created)", node.getwalletinfo)
 
         self.log.info("Load first wallet")
         loadwallet_name = node.loadwallet(wallet_names[0])
@@ -316,7 +316,7 @@ def wallet_file(name):
         for wallet_name in self.nodes[0].listwallets():
             self.nodes[0].unloadwallet(wallet_name)
         assert_equal(self.nodes[0].listwallets(), [])
-        assert_raises_rpc_error(-32601, "Method not found (wallet method is disabled because no wallet is loaded)", self.nodes[0].getwalletinfo)
+        assert_raises_rpc_error(-18, "No wallet is loaded. Load a wallet using loadwallet or create a new one with createwallet. (Note: A default wallet is no longer automatically created)", self.nodes[0].getwalletinfo)
 
         # Successfully load a previously unloaded wallet
         self.nodes[0].loadwallet('w1')