Merge #20161: Minor Taproot follow-ups

1d22300 Address functional test nits (Pieter Wuille)
5669642 docs: mention BIPs 340-342 in doc/bips.md (Pieter Wuille)

Pull request description:

  This addresses some nits in the tests, and adds entries for BIP 340-342 to doc/bips.md.

ACKs for top commit:
  fanquake:
    ACK 1d22300
  benthecarman:
    ACK 1d22300

Tree-SHA512: ad8f937dc6a34db86c585f65beb80e7eceda1822d9a20c86346a319908870381062856d0b95b42049a2791317a038c77fbcbf896c9f4aaa7318e4864b7fcf7a4

Author: fanquake

doc/bips.md

@@ -45,3 +45,4 @@ BIPs that are implemented by Bitcoin Core (up-to-date up to **v0.21.0**):
 * [`BIP 176`](https://github.com/bitcoin/bips/blob/master/bip-0176.mediawiki): Bits Denomination [QT only] is supported as of **v0.16.0** ([PR 12035](https://github.com/bitcoin/bitcoin/pull/12035)).
 * [`BIP 325`](https://github.com/bitcoin/bips/blob/master/bip-0325.mediawiki): Signet test network is supported as of **v0.21.0** ([PR 18267](https://github.com/bitcoin/bitcoin/pull/18267)).
 * [`BIP 339`](https://github.com/bitcoin/bips/blob/master/bip-0339.mediawiki): Relay of transactions by wtxid is supported as of **v0.21.0** ([PR 18044](https://github.com/bitcoin/bitcoin/pull/18044)).
+* [`BIP 340`](https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki) [`341`](https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki) [`342`](https://github.com/bitcoin/bips/blob/master/bip-0342.mediawiki): Validation rules for Taproot (including Schnorr signatures and Tapscript leaves) are implemented as of **v0.21.0** ([PR 19953](https://github.com/bitcoin/bitcoin/pull/19953)), without mainnet activation.

test/functional/test_framework/key.py

@@ -240,8 +240,8 @@ def set(self, data):
             x = int.from_bytes(data[1:33], 'big')
             if SECP256K1.is_x_coord(x):
                 p = SECP256K1.lift_x(x)
-                # if the oddness of the y co-ord isn't correct, find the other
-                # valid y
+                # Make the Y coordinate odd if required (lift_x always produces
+                # a point with an even Y coordinate).
                 if data[0] & 1:
                     p = SECP256K1.negate(p)
                 self.p = p
@@ -542,7 +542,7 @@ def test_schnorr_testvectors(self):
                         sig_actual = sign_schnorr(seckey, msg, aux_rand)
                         self.assertEqual(sig.hex(), sig_actual.hex(), "BIP340 test vector %i (%s): sig mismatch" % (i, comment))
                     except RuntimeError as e:
-                        self.assertFalse("BIP340 test vector %i (%s): signing raised exception %s" % (i, comment, e))
+                        self.fail("BIP340 test vector %i (%s): signing raised exception %s" % (i, comment, e))
                 result_actual = verify_schnorr(pubkey, sig, msg)
                 if result:
                     self.assertEqual(result, result_actual, "BIP340 test vector %i (%s): verification failed" % (i, comment))