text: 
  
  TITLE
  [trainer] deepspeed bug fixes and tests
  
  COMMENTS
  3
  
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  BODY
  This PR:
  * fixes a bug with `model.no_sync()` which is not supported by DeepSpeed - we had the test but it's not running on CI 
  * fixes a bug with when `--train` is not used - have to `.to(device)` in that case - reported here (https://github.com/huggingface/transformers/issues/9996#issuecomment-774232901)
  * splits the deepspeed tests into its own dedicated file and will slowly start to build it up - but it's good enough for now - especially since we are going to switch over `run_seq2seq.py`, except it's not fully ready yet for adoption.
  * adds a new test which doesn't use `--train`
  
  @sgugger 