 segmentation fault (core dumped)  proxychains4 python xxx.py
## Environment info
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     Don't forget to fill out the missing fields in that output! -->
     
- `transformers` version: 3.4.0
- Platform: ubuntu 18.04
- Python version: 3.6
- PyTorch version (GPU?): 1.4.0 GPU
- Tensorflow version (GPU?): 2.2.0 GPU
- Using GPU in script?: yes
- Using distributed or parallel set-up in script?: no
- Network: need to use http proxy to download files and I use the tool ProxyChains4 


## To reproduce

Steps to reproduce the behavior:

1. Save the following code to file test.py

```python

from transformers import pipeline

classifier = pipeline('sentiment-analysis')


classifier('We are very happy to include pipeline into the transformers repository.')

```

2.  Exec `proxychains4 python test.py`
3. The following error was raised

```shell
(test) ➜  test-transformer proxychains4 python test.py
[proxychains] config file found: /etc/proxychains4.conf
[proxychains] preloading /usr/lib/x86_64-linux-gnu/libproxychains.so.4
[proxychains] DLL init: proxychains-ng 4.12
[proxychains] DLL init: proxychains-ng 4.12
[proxychains] Strict chain  ...  10.74.193.90:80  ...  s3.amazonaws.com:443  ...  OK
[proxychains] Strict chain  ...  10.74.193.90:80  ...  s3.amazonaws.com:443  ...  OK
[proxychains] Strict chain  ...  10.74.193.90:80  ...  s3.amazonaws.com:443  ...  OK
[proxychains] Strict chain  ...  10.74.193.90:80  ...  s3.amazonaws.com:443  ...  OK
[proxychains] Strict chain  ...  10.74.193.90:80  ...  s3.amazonaws.com:443  ...  OK
[proxychains] Strict chain  ...  10.74.193.90:80  ...  s3.amazonaws.com:443  ...  OK
[proxychains] Strict chain  ...  10.74.193.90:80  ...  s3.amazonaws.com:443  ...  OK
[proxychains] Strict chain  ...  10.74.193.90:80  ...  s3.amazonaws.com:443  ...  OK
[proxychains] Strict chain  ...  10.74.193.90:80  ...  cdn.huggingface.co:443  ...  OK
[1]    9790 segmentation fault (core dumped)  proxychains4 python test.py
```

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## Expected behavior

<!-- A clear and concise description of what you would expect to happen. -->

The model files can be downloaded without error

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