merge bitcoin#21100: remove unused function xor_bytes

Author: kwvg

test/functional/test_framework/key.py

@@ -19,10 +19,6 @@ def TaggedHash(tag, data):
     ss += data
     return hashlib.sha256(ss).digest()
 
-def xor_bytes(b0, b1):
-    assert len(b0) == len(b1)
-    return bytes(x ^ y for (x, y) in zip(b0, b1))
-
 def jacobi_symbol(n, k):
     """Compute the Jacobi symbol of n modulo k
 
@@ -522,7 +518,7 @@ def test_schnorr(self):
             if pubkey is not None:
                 keys[privkey] = pubkey
         for msg in byte_arrays:  # test every combination of message, signing key, verification key
-            for sign_privkey, sign_pubkey in keys.items():
+            for sign_privkey, _ in keys.items():
                 sig = sign_schnorr(sign_privkey, msg)
                 for verify_privkey, verify_pubkey in keys.items():
                     if verify_privkey == sign_privkey: