test is creating pool before iteration solves ci test problems

dlt/extract/pipe.py

@@ -589,6 +589,7 @@ def _fork_pipeline(pipe: Pipe) -> None:
         return cls(max_parallel_items, workers, futures_poll_interval, sources, next_item_mode)
 
     def __next__(self) -> PipeItem:
+        self._ensure_async_pool()
         pipe_item: Union[ResolvablePipeItem, SourcePipeItem] = None
         # __next__ should call itself to remove the `while` loop and continue clauses but that may lead to stack overflows: there's no tail recursion opt in python
         # https://stackoverflow.com/questions/13591970/does-python-optimize-tail-recursion (see Y combinator on how it could be emulated)