redis 3 monitoring error

[woutervb]

When using the trapper mode of this tool. I received the following exception:

redis.exceptions.ResponseError: WRONGTYPE Operation against a key holding the wrong kind of value

I could narrow this down to the following piece of code:

   keys = client.keys('*')
   llensum = 0
   for key in keys:
           llensum += client.llen(key)
   a.append(Metric(args.hostname, 'redis[llenall]', llensum))

Which seems like the is / can be a problem with the call for llen on a specific key. Putting the code in an try: / except: clause fixed the problem, but return 0 a a value for llenall. So I simply removed the code.

I am not really into redis, but is this problem caused by a change in redis 2 -> 3? Or is there a specific python redis client requirement. I am running version 2.10.1-1 (debian 8 std installation)