rag examples tests fail
```
================================================================ ERRORS =================================================================
______________________________________ ERROR collecting examples/rag/test_distributed_retriever.py ______________________________________
ImportError while importing test module '/Users/shleifer/transformers_fork/examples/rag/test_distributed_retriever.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
examples/rag/test_distributed_retriever.py:26: in <module>
    from examples.rag.distributed_retriever import RagPyTorchDistributedRetriever  # noqa: E402 # isort:skip
E   ModuleNotFoundError: No module named 'examples.rag'
```