message: test: use f-strings in feature_dersig.py
diff: @@ -104,7 +104,7 @@ class BIP66Test(BitcoinTestFramework):
  block.rehash()
  block.solve()
  - with self.nodes[0].assert_debug_log(expected_msgs=['{}, bad-version(0x00000002)'.format(block.hash)]):
  + with self.nodes[0].assert_debug_log(expected_msgs=[f'{block.hash}, bad-version(0x00000002)']):
  peer.send_and_ping(msg_block(block))
  assert_equal(int(self.nodes[0].getbestblockhash(), 16), tip)
  peer.sync_with_ping()
  @@ -134,7 +134,7 @@ class BIP66Test(BitcoinTestFramework):
  block.rehash()
  block.solve()
  - with self.nodes[0].assert_debug_log(expected_msgs=['CheckInputScripts on {} failed with non-mandatory-script-verify-flag (Non-canonical DER signature)'.format(block.vtx[-1].hash)]):
  + with self.nodes[0].assert_debug_log(expected_msgs=[f'CheckInputScripts on {block.vtx[-1].hash} failed with non-mandatory-script-verify-flag (Non-canonical DER signature)']):
  peer.send_and_ping(msg_block(block))
  assert_equal(int(self.nodes[0].getbestblockhash(), 16), tip)
  peer.sync_with_ping()
  