Stop using USE <keyspace> with prepared statements
This caused the following warning:
WARNING cassandra.protocol:libevreactor.py:361 Server warning: `USE <keyspace>` with prepared statements is considered to be an anti-pattern due to ambiguity in non-qualified table names. Please consider removing instances of `Session#setKeyspace(<keyspace>)`, `Session#execute("USE <keyspace>")` and `cluster.newSession(<keyspace>)` from your code, and always use fully qualified table names (e.g. <keyspace>.<table>).This also prepends 'test' to the name of keyspaces used in tests, so
they are guaranteed to start with an letter (starting with digits cause
syntax errors in most statements).