42e1b5d [test] Round target fee to 8 decimals in assert_fee_amount (Karl-Johan Alm)
Pull request description:
The output would produce arbitrary number of decimal points, sometimes resulting in 9 decimals:
```
AssertionError: Fee of 0.00000415 BTC too low! (Should be 0.000006175 BTC)
```
The above looks like the expected fee is 6175 sats when in reality it's 618.
Tree-SHA512: ddbff2926a88890d6e34a58db36f0b15a917a80064be6e40e9bcbec3f05ae6202d02adcd7873733945b043fa121d4a56dd930446ec368078fe1935cbfff898ce