If the error is not handled, the running daemon will continuously
print the following error message:
```
Traceback (most recent call last):
File "lbry/extras/daemon/exchange_rate_manager.py", line 77, in get_rate
File "lbry/extras/daemon/exchange_rate_manager.py", line 189, in get_rate_from_response
KeyError: 0
```
This started happening when the UPBit exchange decided to delist
the LBC coin.
Normally `json_response` should be a dictionary, not a list,
so `json_response[0]` causes an error.
By checking for the `'error'` key, we can raise the proper exception.
Once this is done, the message will be a warning, not a traceback.
```
WARNING lbry.extras.daemon.exchange_rate_manager:92:
Failed to get exchange rate from UPbit: result not found
```
