Comment 9 for bug 1866008

According to your previous email on the ML I put the traceback that you pointed out:

```
The error is TypeError: __init__() got an unexpected keyword argument
'dead_retry'
```

I think our issue is due to the fact that python-memcached accept a param named `dead_retry` [1] which is not defined in pymemcache.

We just need to define it in our oslo.cache mapping. During testing we faced the same kind of issue with connection timeout.

[1] https://github.com/linsomniac/python-memcached/blob/bad41222379102e3f18f6f2f7be3ee608de6fbff/memcache.py#L183
[2] https://github.com/openstack/oslo.cache/blob/8a8248d764bbb1db6c0089a58745803c03e38fdb/oslo_cache/_memcache_pool.py#L193,L201