rpc: update min package size error message in submitpackage

Currently, the only allowed package topology has a min size of 2.
Update the error message to reflect that.

Author: stickies-v

src/rpc/mempool.cpp

@@ -861,9 +861,9 @@ static RPCHelpMan submitpackage()
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
         {
             const UniValue raw_transactions = request.params[0].get_array();
-            if (raw_transactions.size() < 1 || raw_transactions.size() > MAX_PACKAGE_COUNT) {
+            if (raw_transactions.size() < 2 || raw_transactions.size() > MAX_PACKAGE_COUNT) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER,
-                                   "Array must contain between 1 and " + ToString(MAX_PACKAGE_COUNT) + " transactions.");
+                                   "Array must contain between 2 and " + ToString(MAX_PACKAGE_COUNT) + " transactions.");
             }
 
             std::vector<CTransactionRef> txns;

test/functional/rpc_packages.py

@@ -343,10 +343,10 @@ def test_submitpackage(self):
         assert_raises_rpc_error(-25, "package topology disallowed", node.submitpackage, chain_hex)
         assert_equal(legacy_pool, node.getrawmempool())
 
-        assert_raises_rpc_error(-8, f"Array must contain between 1 and {MAX_PACKAGE_COUNT} transactions.", node.submitpackage, [])
-        assert_raises_rpc_error(-25, "package topology disallowed", node.submitpackage, [chain_hex[0]] * 1)
+        assert_raises_rpc_error(-8, f"Array must contain between 2 and {MAX_PACKAGE_COUNT} transactions.", node.submitpackage, [])
+        assert_raises_rpc_error(-8, f"Array must contain between 2 and {MAX_PACKAGE_COUNT} transactions.", node.submitpackage, [chain_hex[0]] * 1)
         assert_raises_rpc_error(
-            -8, f"Array must contain between 1 and {MAX_PACKAGE_COUNT} transactions.",
+            -8, f"Array must contain between 2 and {MAX_PACKAGE_COUNT} transactions.",
             node.submitpackage, [chain_hex[0]] * (MAX_PACKAGE_COUNT + 1)
         )