[Bloom] Fix hangs of bloom test

[k-artem]

test_checkpoint_sharding.py::TestCheckpointShard::test[bigscience/bloom-560m-fp16] silently hangs if incorrect version of transformers(>4.43.4) is installed, due to no proper handling of SystemExit in the pool worker.

Fix is throw RuntimeError instead of sys.exit.

• Test:
  Run pytest tests/unit/inference/test_checkpoint_sharding.py -k 'bloom-560m-fp16'

• Result: no hangs, throw exception:

E           RuntimeError: Transformers version 4.57.3 exceeds version 4.43.4! After transformers version 4.43.4, BLOOM inference with DeepSpeed is no longer supported.

/usr/lib/python3.12/multiprocessing/pool.py:774: RuntimeError

[PKUWZP]

Thanks for sending the fix. This PR fixes a test hang in test_checkpoint_sharding.py for the BLOOM 560m model. The root cause is that sys.exit() is called inside a multiprocessing pool worker when an incompatible transformers version is detected. sys.exit() raises SystemExit, which multiprocessing.Pool does not propagate back to the parent process cleanly — it silently hangs instead. The fix replaces sys.exit() with raise RuntimeError(...), which is properly caught and re-raised by the pool.

If @loadams and @hwchen2017 do not have questions I approve this PR fix.