rpc: Return wtxid from testmempoolaccept

test/functional/feature_dersig.py

@@ -112,8 +112,13 @@ class BIP66Test(BitcoinTestFramework):
         # First we show that this tx is valid except for DERSIG by getting it
         # rejected from the mempool for exactly that reason.
         assert_equal(
-            [{'txid': spendtx.hash, 'allowed': False, 'reject-reason': 'non-mandatory-script-verify-flag (Non-canonical DER signature)'}],
-            self.nodes[0].testmempoolaccept(rawtxs=[spendtx.serialize().hex()], maxfeerate=0)
+            [{
+                'txid': spendtx.hash,
+                'wtxid': spendtx.getwtxid(),
+                'allowed': False,
+                'reject-reason': 'non-mandatory-script-verify-flag (Non-canonical DER signature)',
+            }],
+            self.nodes[0].testmempoolaccept(rawtxs=[spendtx.serialize().hex()], maxfeerate=0),
         )
 
         # Now we verify that a block with this transaction is also invalid.