There is a fee error somewhere

[bonomat]

Random error recorded:

1. Borrower took a loan
2. Signing worked
3. Sent to Bobtimus
4. Bobtimus failed

2021-07-30T00:12:20.032501Z  INFO Server::run{addr=127.0.0.1:3030}: warp::server: listening on http://127.0.0.1:3030
2021-07-30T05:10:36.390841Z ERROR bobtimus::problem: unhandled error: JSON-RPC request failed with code -26: insufficient fee, rejecting replacement 2e3a4d00a38e57612d0ab06124ad5a04666110264b669780f6a0c1812976d7f6; new feerate 0.00001004 BTC/kB <= old feerate 0.00001004 BTC/kB (code 66): JSON-RPC request failed with code -26: insufficient fee, rejecting replacement 2e3a4d00a38e57612d0ab06124ad5a04666110264b669780f6a0c1812976d7f6; new feerate 0.00001004 BTC/kB <= old feerate 0.00001004 BTC/kB (code 66)

5. Borrower thinks the loan is active.

Loan values.

[bonomat]

This issue stems from bobtimus trying to double spend himself:

How to reproduce:

• take 1 loan (don't repay)
• take another loan

the second loan creation might fail. If not, keep taking loans :D
Eventually bobtimus runs out of utxo's and will double spend a transaction.
This fails with the error:

new feerate 0.00001004 BTC/kB <= old feerate 0.00001004 BTC/kB

Meaning, it assumes a replace by fee but since we use the same fee again the second transaction fails.

[bonomat]

Issue on Bobtimus side is that we do not lock selected utxos:

waves/bobtimus/src/lib.rs

Lines 132 to 135 in f366dd9

	let bob_inputs = elements_client
	.select_inputs_for(asset_id, input_amount, false)
	.await
	.context("failed to select inputs for swap")?;

So this might be an easy fix.
Besides that, we should nevertheless report an error to the caller if publishing failed.