test: let gen_return_txouts create a single large OP_RETURN output

Transactions with more than one datacarrier (OP_RETURN) output
are never considered standard, i.e. this change is necessary in
order to to get rid of the `acceptnonstdtxn` option for some
tests.

Author: theStack

test/functional/test_framework/util.py

@@ -502,20 +502,9 @@ def chain_transaction(node, parent_txids, vouts, value, fee, num_outputs):
 # to make it large (helper for constructing large transactions). The
 # total serialized size of the txouts is about 66k vbytes.
 def gen_return_txouts():
-    # Some pre-processing to create a bunch of OP_RETURN txouts to insert into transactions we create
-    # So we have big transactions (and therefore can't fit very many into each block)
-    # create one script_pubkey
-    script_pubkey = "6a4d0200"  # OP_RETURN OP_PUSH2 512 bytes
-    for _ in range(512):
-        script_pubkey = script_pubkey + "01"
-    # concatenate 128 txouts of above script_pubkey which we'll insert before the txout for change
-    txouts = []
     from .messages import CTxOut
-    txout = CTxOut()
-    txout.nValue = 0
-    txout.scriptPubKey = bytes.fromhex(script_pubkey)
-    for _ in range(128):
-        txouts.append(txout)
+    from .script import CScript, OP_RETURN
+    txouts = [CTxOut(nValue=0, scriptPubKey=CScript([OP_RETURN, b'\x01'*67437]))]
     assert_equal(sum([len(txout.serialize()) for txout in txouts]), 67456)
     return txouts