refactor: move helper `random_bytes` to util library

Can be easily reviewed with `--color-moved=dimmed-zebra`.

test/functional/feature_taproot.py

@@ -91,7 +91,11 @@ from test_framework.script_util import (
     script_to_p2wsh_script,
 )
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_raises_rpc_error, assert_equal
+from test_framework.util import (
+    assert_raises_rpc_error,
+    assert_equal,
+    random_bytes,
+)
 from test_framework.key import generate_privkey, compute_xonly_pubkey, sign_schnorr, tweak_add_privkey, ECKey
 from test_framework.address import (
     hash160,
@@ -566,10 +570,6 @@ def random_checksig_style(pubkey):
         ret = CScript([pubkey, opcode])
     return bytes(ret)
 
-def random_bytes(n):
-    """Return a random bytes object of length n."""
-    return bytes(random.getrandbits(8) for i in range(n))
-
 def bitflipper(expr):
     """Return a callable that evaluates expr and returns it with a random bitflip."""
     def fn(ctx):

test/functional/test_framework/util.py

@@ -12,6 +12,7 @@ import inspect
 import json
 import logging
 import os
+import random
 import re
 import time
 import unittest
@@ -286,6 +287,13 @@ def sha256sum_file(filename):
             d = f.read(4096)
     return h.digest()
 
+
+# TODO: Remove and use random.randbytes(n) instead, available in Python 3.9
+def random_bytes(n):
+    """Return a random bytes object of length n."""
+    return bytes(random.getrandbits(8) for i in range(n))
+
+
 # RPC/P2P connection constants and functions
 ############################################