sentencepiece 0.1.94 causing segmentation fault
## Environment info
<!-- You can run the command `transformers-cli env` and copy-and-paste its output below.
     Don't forget to fill out the missing fields in that output! -->
     
- `transformers` version: 3.4.0 and 3.3.1
- Platform: Linux/Sagemaker
- Python version: 3.7
- PyTorch version (GPU?): 1.4
- Tensorflow version (GPU?): 
- Using GPU in script?: No
- Using distributed or parallel set-up in script?: No

### Who can help

## Information

## To reproduce

Steps to reproduce the behavior:

1. `pip install transformers[torch]`
2. `from transformers.trainer import TrainingArguments, Trainer`
`import torch`
3. `torch.tensor([1,2,3])`

`transformers` 3.3.1 seg faults at step 3, `transformers` 3.4 seg faults at step 2.

## Expected behavior

No segmentation fault
This can be worked around, for anyone hitting this issue, by setting `sentencepiece==0.1.91` explicitly.<|||||>Maybe we could set `sentencepiece==0.1.91` in the setup.py to prevent this from happening, as we already had the issue with the 0.1.92.

Do you want to open a PR for that?<|||||>This should also be fixed by #8073 <|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
