You didn't set `gas`

I was getting:
```
web3.exceptions.ContractLogicError: execution reverted: TransferHelper: TRANSFER_FROM_FAILED
```
on BUNNY -> WETH

Adding gas fixed it:
```
).buildTransaction({
    'from': config.MY_WALLET_ADDRESS,
    'gas': 250000,
    'gasPrice': web3.toWei('5','gwei'),
    'nonce': web3.eth.get_transaction_count(config.MY_WALLET_ADDRESS),
})
```