conda install transformers (not working) behaving differently from pip install transformers (working) for CentOS 7.9
A fresh environment where I `conda install pytorch torchvision torchaudio -c pytorch` then `conda install transformers` produces a glibc2.18 error on CentOS 7.9 upon import with `python -c "from transformers import AutoTokenizer"`. I suspect this is a similar error to #2980, i.e., CentOS 7.9 might just be incompatible. However, a different fresh environment where I `pip install torch torchvision torchaudio` then `pip install transformers` does not produce any error upon import with `python -c "from transformers import AutoTokenizer"`. 



## Environment info (pip-installed)
<!-- 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: 4.4.2
- Platform: Linux-4.19.182-1.el7.retpoline.x86_64-x86_64-with-glibc2.10
- Python version: 3.8.8
- PyTorch version (GPU?): 1.8.1+cu102 (True)
- Tensorflow version (GPU?): not installed (NA)
- Using GPU in script?: N/A
- Using distributed or parallel set-up in script?: <fill in>

## Environment info (conda-installed)
In fact, this command doesn't even work. See attached `cli_error_trace.txt`.

### Who can help

I'm not sure if I did this right since this seems to be more of a lower-level issue than implementation issue.

-huggingface/transformers/blob/master/src/transformers/models/auto/tokenization_auto.py @LysandreJik 

## Information

Model I am using (Bert, XLNet ...):

N/A

## To reproduce

This is all done on CentOS 7.9.

##### Steps to reproduce the good, pip-installed behavior:

1. conda create --name test python=3.8
2. conda activate test
3. pip install torch torchvision torchaudio
4. pip install transformers
5. python -c "from transformers import AutoTokenizer"

##### Steps to reproduce the bad, conda-installed behavior:
1. conda create --name test2 python=3.8
2. conda activate test2
3. conda install pytorch torchvision torchaudio -c pytorch
4. conda install -c huggingface transformers
5. python -c "from transformers import AutoTokenizer"

Additionally, I have attached the `environment.yml` files for both environments and also the trace for the `transformers-cli env` command and the trace for the import error (both for the `conda install`-ed environment). The traces look pretty similar, and it seems the issue is with the dependencies of tokenizers. The .yml files have an appended .txt extension since apparently GitHub doesn't support the .yml extension for uploaded files.

[environment_pip.yml.txt](https://github.com/huggingface/transformers/files/6239328/environment_pip.yml.txt)
[environment_conda.yml.txt](https://github.com/huggingface/transformers/files/6239327/environment_conda.yml.txt)
[cli_error_trace.txt](https://github.com/huggingface/transformers/files/6239326/cli_error_trace.txt)
[import_error_trace.txt](https://github.com/huggingface/transformers/files/6239329/import_error_trace.txt)

## Expected behavior

I would expect `conda install`-ing and `pip install`-ing to both work as intended.
Hello! From what I'm seeing, the error comes from the `tokenizers` library instead:
```
[...]
  File "/homes/gws/hcybay/miniconda3/envs/test2/lib/python3.8/site-packages/transformers-4.4.2-py3.8.egg/transformers/tokenization_utils_fast.py", line 25, in <module>
  File "/homes/gws/hcybay/miniconda3/envs/test2/lib/python3.8/site-packages/tokenizers/__init__.py", line 79, in <module>
    from .tokenizers import (
ImportError: /lib64/libc.so.6: version `GLIBC_2.18' not found (required by /homes/gws/hcybay/miniconda3/envs/test2/lib/python3.8/site-packages/tokenizers/tokenizers.cpython-38-x86_64-linux-gnu.so)
```

Do you mind opening an issue there? They'll probably be able to help out better.<|||||>Sure--sorry, didn't know which to open it in<|||||>Looks like I definitely should've searched the issues there first... https://github.com/huggingface/tokenizers/issues/585