wallet: fix SetFeeEstimateMode() error message

to clarify for the user the confusing error message that the missing fee rate
needs to be set in the conf_target param/option.

Author: jonatack

src/wallet/rpcwallet.cpp

@@ -214,7 +214,7 @@ static void SetFeeEstimateMode(const CWallet* pwallet, CCoinControl& cc, const U
 
     if (cc.m_fee_mode == FeeEstimateMode::BTC_KB || cc.m_fee_mode == FeeEstimateMode::SAT_B) {
         if (estimate_param.isNull()) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "Selected estimate_mode requires a fee rate");
+            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Selected estimate_mode %s requires a fee rate to be specified in conf_target", estimate_mode.get_str()));
         }
 
         CAmount fee_rate = AmountFromValue(estimate_param);

test/functional/wallet_basic.py

@@ -228,7 +228,7 @@ def run_test(self):
 
         # Sendmany with explicit fee (BTC/kB)
         # Throw if no conf_target provided
-        assert_raises_rpc_error(-8, "Selected estimate_mode requires a fee rate",
+        assert_raises_rpc_error(-8, "Selected estimate_mode bTc/kB requires a fee rate to be specified in conf_target",
             self.nodes[2].sendmany,
             amounts={ address: 10 },
             estimate_mode='bTc/kB')
@@ -254,7 +254,7 @@ def run_test(self):
 
         # Sendmany with explicit fee (SAT/B)
         # Throw if no conf_target provided
-        assert_raises_rpc_error(-8, "Selected estimate_mode requires a fee rate",
+        assert_raises_rpc_error(-8, "Selected estimate_mode sat/b requires a fee rate to be specified in conf_target",
             self.nodes[2].sendmany,
             amounts={ address: 10 },
             estimate_mode='sat/b')
@@ -421,7 +421,7 @@ def run_test(self):
             assert prebalance > 2
             address = self.nodes[1].getnewaddress()
             # Throw if no conf_target provided
-            assert_raises_rpc_error(-8, "Selected estimate_mode requires a fee rate",
+            assert_raises_rpc_error(-8, "Selected estimate_mode BTc/Kb requires a fee rate to be specified in conf_target",
                 self.nodes[2].sendtoaddress,
                 address=address,
                 amount=1.0,
@@ -455,7 +455,7 @@ def run_test(self):
             assert prebalance > 2
             address = self.nodes[1].getnewaddress()
             # Throw if no conf_target provided
-            assert_raises_rpc_error(-8, "Selected estimate_mode requires a fee rate",
+            assert_raises_rpc_error(-8, "Selected estimate_mode SAT/b requires a fee rate to be specified in conf_target",
                 self.nodes[2].sendtoaddress,
                 address=address,
                 amount=1.0,