Segmentation fault when GPT2-chinese import transformers
Author: jstzwj
Pull request: no

## ❓ Questions & Help
CPU: Intel(R) Xeon(R) CPU E5-2680 v4 @ 2.40GHz
GPU: Tesla P40
OS Platform: Ubuntu 16.04.3 LTS
transformers version: 2.2.2
TensorFlow version: 2.0.0
PyTorch version: 1.3.1
Python version: 3.6.2

Hi
When I trained the model in [GPT2-chinese](https://github.com/Morizeyao/GPT2-Chinese), it imported transformers and got an error - Segmentation fault(core dumped)
```
(python36) user@ubuntu:~/projects/GPT2-Chinese$ python -Xfaulthandler train.py
I1218 00:39:09.690756 139724474922816 file_utils.py:33] TensorFlow version 2.0.0 available.
Fatal Python error: Segmentation fault

Current thread 0x00007f1423b1b740 (most recent call first):
  File "<frozen importlib._bootstrap>", line 205 in _call_with_frames_removed
  File "<frozen importlib._bootstrap_external>", line 922 in create_module
  File "<frozen importlib._bootstrap>", line 560 in module_from_spec
  File "<frozen importlib._bootstrap>", line 648 in _load_unlocked
  File "<frozen importlib._bootstrap>", line 950 in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 961 in _find_and_load
  File "/home/wangjun/.conda/envs/python36/lib/python3.6/site-packages/torch/__init__.py", line 81 in <module>
  File "<frozen importlib._bootstrap>", line 205 in _call_with_frames_removed
  File "<frozen importlib._bootstrap_external>", line 678 in exec_module
  File "<frozen importlib._bootstrap>", line 655 in _load_unlocked
  File "<frozen importlib._bootstrap>", line 950 in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 961 in _find_and_load
  File "/home/wangjun/.conda/envs/python36/lib/python3.6/site-packages/transformers/file_utils.py", line 38 in <module>
  File "<frozen importlib._bootstrap>", line 205 in _call_with_frames_removed
  File "<frozen importlib._bootstrap_external>", line 678 in exec_module
  File "<frozen importlib._bootstrap>", line 655 in _load_unlocked
  File "<frozen importlib._bootstrap>", line 950 in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 961 in _find_and_load
  File "/home/wangjun/.conda/envs/python36/lib/python3.6/site-packages/transformers/__init__.py", line 20 in <module>
  File "<frozen importlib._bootstrap>", line 205 in _call_with_frames_removed
  File "<frozen importlib._bootstrap_external>", line 678 in exec_module
  File "<frozen importlib._bootstrap>", line 655 in _load_unlocked
  File "<frozen importlib._bootstrap>", line 950 in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 961 in _find_and_load
  File "train.py", line 1 in <module>
Segmentation fault (core dumped)
```
So I found the error came from line 33 'import torch' in 'transformers/transformers/file_utils.py'.  
Then I swapped the position where tensorflow and torch are imported and the error disappeared.  
I wonder whether it is a bug of transformer or torch and what caused it.  


Comments:
Is it related to #2204 ?
**Segmentation fault** (usually) means that you tried to access memory that you do not have access to.

> Is it related to #2204 ?

Yes, it looks like the same bug as this. I know how to solve it but do not know why.😂
![image](https://user-images.githubusercontent.com/13167278/71016852-b8280a00-2130-11ea-9f6d-e545fe2e73a3.png)



Solved in #2207 

@jstzwj I'm still getting this issue on "transformers==2.2.2" on PyPi, how to solve it?

> @jstzwj I'm still getting this issue on "transformers==2.2.2" on PyPi, how to solve it?

#2207