Add a RetryError for all connection failures

[noudin-ledger]

Instead of re-raising the error when the max_retries has been reached, raising a newly created RetryError would allow an easier catching of those specific cases in custom clients or client calls.
It could be for example used as such:

except (ConnectError, ConnectTimeout) as err:
	if retries_left <= 0:
    	raise RetryError from err