sauron: crash on fee estimation

[darosior]

2021-09-13T10:55:49.308Z **BROKEN** lightningd: /home/lightningd/.lightning/plugins/sauron/sauron.py error: bad response to estimatefees (bad 'result' field), response was {"jsonrpc": "2.0", "id": 113037, "error": {"code": -32600, "message": "Error while processing estimatefees: '2'", "traceback": "Traceback (most recent call last):\n  File \"/home/lightningd/.local/lib/python3.9/site-packages/pyln/client/plugin.py\", line 564, in _dispatch_request\n    result = self._exec_func(method.func, request)\n  File \"/home/lightningd/.local/lib/python3.9/site-packages/pyln/client/plugin.py\", line 549, in _exec_func\n    return func(*ba.args, **ba.kwargs)\n  File \"/home/lightningd/.lightning/plugins/sauron/sauron.py\", line 199, in estimatefees\n    very_urgent = int(feerates[\"2\"] * 10**3)\nKeyError: '2'\n"}}

[darosior]

Ok, we need to check indexes there: https://github.com/lightningd/plugins/blob/c4a1a70afe55ae3d6a14bf3c745217ca07fef218/sauron/sauron.py#L180-L184