test: feature_cltv.py: don't return tx copies in modification functions

The functions cltv_modify_tx(), cltv_invalidate() and cltv_validate()
all modify the passed transaction in-place, i.e. there is no need
to return a copy.

Author: theStack

test/functional/feature_cltv.py

@@ -45,7 +45,6 @@ def cltv_modify_tx(tx, prepend_scriptsig, nsequence=None, nlocktime=None):
 
     tx.vin[0].scriptSig = CScript(prepend_scriptsig + list(CScript(tx.vin[0].scriptSig)))
     tx.rehash()
-    return tx
 
 
 def cltv_invalidate(tx, failure_reason):
@@ -69,14 +68,14 @@ def cltv_invalidate(tx, failure_reason):
         [[CScriptNum(500),  OP_CHECKLOCKTIMEVERIFY, OP_DROP], 0xffffffff, 500],
     ][failure_reason]
 
-    return cltv_modify_tx(tx, prepend_scriptsig=scheme[0], nsequence=scheme[1], nlocktime=scheme[2])
+    cltv_modify_tx(tx, prepend_scriptsig=scheme[0], nsequence=scheme[1], nlocktime=scheme[2])
 
 
 def cltv_validate(tx, height):
     # Modify the signature in vin 0 and nSequence/nLockTime of the tx to pass CLTV
     scheme = [[CScriptNum(height), OP_CHECKLOCKTIMEVERIFY, OP_DROP], 0, height]
 
-    return cltv_modify_tx(tx, prepend_scriptsig=scheme[0], nsequence=scheme[1], nlocktime=scheme[2])
+    cltv_modify_tx(tx, prepend_scriptsig=scheme[0], nsequence=scheme[1], nlocktime=scheme[2])
 
 
 class BIP65Test(BitcoinTestFramework):
@@ -114,7 +113,7 @@ def run_test(self):
         invalid_cltv_txs = []
         for i in range(5):
             spendtx = wallet.create_self_transfer(from_node=self.nodes[0])['tx']
-            spendtx = cltv_invalidate(spendtx, i)
+            cltv_invalidate(spendtx, i)
             invalid_cltv_txs.append(spendtx)
 
         tip = self.nodes[0].getbestblockhash()
@@ -149,7 +148,7 @@ def run_test(self):
         # create and test one invalid tx per CLTV failure reason (5 in total)
         for i in range(5):
             spendtx = wallet.create_self_transfer(from_node=self.nodes[0])['tx']
-            spendtx = cltv_invalidate(spendtx, i)
+            cltv_invalidate(spendtx, i)
 
             expected_cltv_reject_reason = [
                 "non-mandatory-script-verify-flag (Operation not valid with the current stack size)",
@@ -182,7 +181,7 @@ def run_test(self):
                 peer.sync_with_ping()
 
         self.log.info("Test that a version 4 block with a valid-according-to-CLTV transaction is accepted")
-        spendtx = cltv_validate(spendtx, CLTV_HEIGHT - 1)
+        cltv_validate(spendtx, CLTV_HEIGHT - 1)
 
         block.vtx.pop(1)
         block.vtx.append(spendtx)