Summarization pipeline fails to initialize
# 🐛 Bug

## Information

Model I am using (T5):

Language I am using the model on (Englis):

The problem arises when using:
* [+] the official example scripts: (give details below)
https://huggingface.co/transformers/main_classes/pipelines.html#transformers.SummarizationPipeline
* [ ] my own modified scripts: (give details below)

The tasks I am working on is:
* [ ] an official GLUE/SQUaD task: (give the name)
* [ ] my own task or dataset: (give details below)

## To reproduce

Steps to reproduce the behavior:
```
from transformers import pipeline
summarizer = pipeline("summarization", model="t5-base", tokenizer="t5-base")
```
Produces the error:

```
Downloading: 100%|██████████| 230/230 [00:00<00:00, 231kB/s]
Couldn't reach server at 'https://s3.amazonaws.com/models.huggingface.co/bert/t5-base-modelcard.json' to download model card file.
Creating an empty model card.
Traceback (most recent call last):
  File "D:\anaconda3\envs\gpt2\lib\site-packages\transformers\configuration_utils.py", line 243, in get_config_dict
    raise EnvironmentError
OSError
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "D:\anaconda3\envs\gpt2\lib\site-packages\IPython\core\interactiveshell.py", line 3331, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-42-1a545b8d35ed>", line 1, in <module>
    summarizer = pipeline("summarization", model="t5-base", tokenizer="t5-base")
  File "D:\anaconda3\envs\gpt2\lib\site-packages\transformers\pipelines.py", line 1423, in pipeline
    model = model_class.from_pretrained(model, config=config, **model_kwargs)
  File "D:\anaconda3\envs\gpt2\lib\site-packages\transformers\modeling_utils.py", line 434, in from_pretrained
    **kwargs,
  File "D:\anaconda3\envs\gpt2\lib\site-packages\transformers\configuration_utils.py", line 192, in from_pretrained
    config_dict, kwargs = cls.get_config_dict(pretrained_model_name_or_path, **kwargs)
  File "D:\anaconda3\envs\gpt2\lib\site-packages\transformers\configuration_utils.py", line 262, in get_config_dict
    raise EnvironmentError(msg)
OSError: Can't load 't5-base'. Make sure that:
- 't5-base' is a correct model identifier listed on 'https://huggingface.co/models'
- or 't5-base' is the correct path to a directory containing a 'config.json' file
```
## Expected behavior
No exception

## Environment info

- `transformers` version: 2.6.0
- Platform: Windows
- Python version: 3,7
- PyTorch version (GPU?): 1.4.0
- Tensorflow version (GPU?): 2.1.0
- Using GPU in script?: No
- Using distributed or parallel set-up in script?:

You're using `transformers` version **2.6.0**, but T5 model was released in version **2.7.0**.

Update your library with :

`pip install --upgrade transformers`<|||||>Thanks, error is not reproduced in 2.8.0