Passing a str Enum to `from_pretrained` gives OSError
Author: rsmith49
Pull request: no

### System Info

Python version 3.8
`transformers==4.28.1`
Ubuntu

### Who can help?

_No response_

### Information

- [ ] The official example scripts
- [X] My own modified scripts

### Tasks

- [ ] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...)
- [X] My own task or dataset (give details below)

### Reproduction

When using a str Enum (as specified [here](https://docs.python.org/3.10/library/enum.html#others) in the python docs) as input to `AutoTokenizer.from_pretrained`, the model name that gets searched is different from the member value of the Enum. Example to repro:

```
from enum import Enum
from transformers import AutoTokenizer

class Tmp(str, Enum):
    BERT = 'bert-base-uncased'

t = AutoTokenizer.from_pretrained(Tmp.BERT)
```

Error:
```
Traceback (most recent call last):
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/huggingface_hub/utils/_errors.py", line 259, in hf_raise_for_status
    response.raise_for_status()
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/requests/models.py", line 1021, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 401 Client Error: Unauthorized for url: https://huggingface.co/Tmp.BERT/resolve/main/tokenizer_config.json

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/transformers/utils/hub.py", line 409, in cached_file
    resolved_file = hf_hub_download(
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/huggingface_hub/utils/_validators.py", line 120, in _inner_fn
    return fn(*args, **kwargs)
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/huggingface_hub/file_download.py", line 1195, in hf_hub_download
    metadata = get_hf_file_metadata(
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/huggingface_hub/utils/_validators.py", line 120, in _inner_fn
    return fn(*args, **kwargs)
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/huggingface_hub/file_download.py", line 1541, in get_hf_file_metadata
    hf_raise_for_status(r)
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/huggingface_hub/utils/_errors.py", line 291, in hf_raise_for_status
    raise RepositoryNotFoundError(message, response) from e
huggingface_hub.utils._errors.RepositoryNotFoundError: 401 Client Error. (Request ID: Root=1-644c4a27-5bd929b32085d52d1a1b4b30)

Repository Not Found for url: https://huggingface.co/Tmp.BERT/resolve/main/tokenizer_config.json.
Please make sure you specified the correct `repo_id` and `repo_type`.
If you are trying to access a private or gated repo, make sure you are authenticated.
Invalid username or password.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/transformers/models/auto/tokenization_auto.py", line 642, in from_pretrained
    tokenizer_config = get_tokenizer_config(pretrained_model_name_or_path, **kwargs)
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/transformers/models/auto/tokenization_auto.py", line 486, in get_tokenizer_config
    resolved_config_file = cached_file(
  File "/home/ubuntu/test_env/lib/python3.8/site-packages/transformers/utils/hub.py", line 424, in cached_file
    raise EnvironmentError(
OSError: Tmp.BERT is not a local folder and is not a valid model identifier listed on 'https://huggingface.co/models'
If this is a private repository, make sure to pass a token having permission to this repo with `use_auth_token` or log in with `huggingface-cli login` and pass `use_auth_token=True`.
```

### Expected behavior

We should see the model being searched for use the string value of the Enum member, instead of a different value (I haven't dug in to see what is being used instead).

Comments:
I'm not sure why you think this should be supported. `str(Tmp.BERT)` is `'Tmp.BERT'`, which is not a valid identifier to pass to `from_pretrained`. You need to pass `Tmp.BERT.value`.

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.