fix rocksdb for use with global tables or tables that use_partitioner (#130)

* fix rocksdb use with global tables or tables that use_partitioner to produce to c
hangelog topics

* fix linting

* fix linting

Co-authored-by: alexanderoberegger <alexander.oberegger@smaxtec.com>

Author: aoberegg

faust/stores/rocksdb.py

@@ -289,7 +289,12 @@ def _open_for_partition(self, partition: int) -> DB:
 
     def _get(self, key: bytes) -> Optional[bytes]:
         event = current_event()
-        if event is not None:
+        partition_from_message = (
+            event is not None
+            and not self.table.is_global
+            and not self.table.use_partitioner
+        )
+        if partition_from_message:
             partition = event.message.partition
             db = self._db_for_partition(partition)
             value = db.get(key)