Greg Sanders helped debug this:
```
# Payment should succeed.
> l1.bitcoin.generate_block(1, wait_for_mempool=txid1)
tests/test_closing.py:2145:
...
> raise ValueError("Timeout while waiting for {}".format(success))
E ValueError: Timeout while waiting for <function BitcoinD.generate_block.<locals>.<lambda> at 0x7f7cd7271560>
```
The lgos show the HTLC tx doesn't go through because it double-spent an input but didn't spend enough:
```
2023-07-06T03:05:54.3424456Z lightningd-2 2023-07-06T02:57:37.490Z DEBUG plugin-bcli: sendrawtx exit 26 (bitcoin-cli -regtest -datadir=/tmp/ltests-yihsd7f4/test_onchain_middleman_simple_1/lightning-2/ -rpcport=39033 -rpcuser=... -stdinrpcpass sendrawtransaction 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) error code: -26\nerror message:\ninsufficient fee, rejecting replacement 76f438f176d8f9beabb286f53c81aa7dcb4948d12f034f51753f4dd9071d6a74; new feerate 0.00029576 BTC/kvB <= old feerate 0.00054659 BTC/kvB
```
This is because sometimes we reuse the same UTXO for the anchor push spend as we do for the HTLC. That would be fine, except that we can have bitcoind mine the commitment tx and not the anchor push, and then we fail to replace it.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
212c4dba76