Can't load `facebook/mbart-large-cc25` tokenizer
# 🐛 Bug
Trying to use the [example](https://huggingface.co/facebook/mbart-large-cc25) fails to load the tokenizer

```
from transformers import AutoTokenizer

tokenizer = AutoTokenizer.from_pretrained("facebook/mbart-large-cc25")
```


## Information

Model I am using `facebook/mbart-large-cc25`



The problem arises when using:
* [ ] the official example scripts: (give details below)
[Example](https://huggingface.co/facebook/mbart-large-cc25) fails to load the tokenizer

```
from transformers import AutoTokenizer

tokenizer = AutoTokenizer.from_pretrained("facebook/mbart-large-cc25")
```

## To reproduce

Steps to reproduce the behavior:

`AutoTokenizer.from_pretrained("facebook/mbart-large-cc25")`

we get the following error indicating a missing model.

```
---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
<ipython-input-48-29412cfd6509> in <module>
----> 1 tokenizer = AutoTokenizer.from_pretrained("facebook/mbart-large-cc25")

/project/WMT20/opt/miniconda3/envs/HuggingFace-3.0.2_cu101/lib/python3.7/site-packages/transformers/tokenization_auto.py in from_pretrained(cls, pretrained_model_name_or_path, *inputs, **kwargs)
    215                     return tokenizer_class_fast.from_pretrained(pretrained_model_name_or_path, *inputs, **kwargs)
    216                 else:
--> 217                     return tokenizer_class_py.from_pretrained(pretrained_model_name_or_path, *inputs, **kwargs)
    218
    219         raise ValueError(

/project/WMT20/opt/miniconda3/envs/HuggingFace-3.0.2_cu101/lib/python3.7/site-packages/transformers/tokenization_utils_base.py in from_pretrained(cls, *inputs, **kwargs)
   1138
   1139         """
-> 1140         return cls._from_pretrained(*inputs, **kwargs)
   1141
   1142     @classmethod

/project/WMT20/opt/miniconda3/envs/HuggingFace-3.0.2_cu101/lib/python3.7/site-packages/transformers/tokenization_utils_base.py in _from_pretrained(cls, pretrained_model_name_or_path, *init_inputs, **kwargs)
   1244                     ", ".join(s3_models),
   1245                     pretrained_model_name_or_path,
-> 1246                     list(cls.vocab_files_names.values()),
   1247                 )
   1248             )

OSError: Model name 'facebook/mbart-large-cc25' was not found in tokenizers model name list (facebook/mbart-large-en-ro, sshleifer/mbart-large-cc25). We assumed 'facebook/mbart-large-cc25' was a path, a model identifier, or url to a directory containing vocabulary files named ['sentencepiece.bpe.model'] but couldn't find such vocabulary files at this path or url.
```

## Expected behavior

Loading a tokenizer for `facebook/mbart-large-cc25` without failure.

## Environment info

```
transformers-cli env
WARNING:tensorflow:From /project/WMT20/opt/miniconda3/envs/HuggingFace-3.0.2_cu101/lib/python3.7/site-packages/transformers/commands/env.py:36: is_gpu_available (from tensorflow.python.framework.test_util) is deprecated and will be removed in a future version.
Instructions for updating:
Use `tf.config.list_physical_devices('GPU')` instead.
2020-07-14 15:14:13.475823: I tensorflow/core/platform/cpu_feature_guard.cc:143] Your CPU supports instructions that this TensorFlow binary was not compiled to use: SSE4.1 SSE4.2 AVX AVX2 AVX512F FMA
2020-07-14 15:14:13.495994: I tensorflow/core/platform/profile_utils/cpu_utils.cc:102] CPU Frequency: 2100000000 Hz
2020-07-14 15:14:13.507620: I tensorflow/compiler/xla/service/service.cc:168] XLA service 0x55555a4d87f0 initialized for platform Host (this does not guarantee that XLA will be used). Devices:
2020-07-14 15:14:13.507676: I tensorflow/compiler/xla/service/service.cc:176]   StreamExecutor device (0): Host, Default Version

Copy-and-paste the text below in your GitHub issue and FILL OUT the two last points.

- `transformers` version: 3.0.2
- Platform: Linux-3.10.0-957.el7.x86_64-x86_64-with-centos-7.8.2003-Core
- Python version: 3.7.6
- PyTorch version (GPU?): 1.5.1 (False)
- Tensorflow version (GPU?): 2.2.0 (False)
- Using GPU in script?: <fill in>
- Using distributed or parallel set-up in script?: <fill in>
```
Should we be using `sshleifer/mbart-large-cc25` has it has a name very similar to `facebook/mbart-large-cc25`?  @sshleifer is the name of a HuggingFace contributor and there could be a rename mismatch.

After downloading both `sshleifer/mbart-large-cc25` and `facebook/mbart-large-cc25`

```
from transformers import AutoTokenizer
model_a = AutoModelWithLMHead.from_pretrained("sshleifer/mbart-large-cc25")
model_b = AutoModelWithLMHead.from_pretrained("facebook/mbart-large-cc25")
```

If we poke at the cache we find that both models have the same sha1sum

```
sha1sum 2593e721f6f9000d1c1a19f144236237dbad3b77d2380982baf030667eaf6f7c.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14{,.json} 31f54e8b3a7628593ed122d67a426dbf6ba0687b3e406d753b61fc3e2d9e5014.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14{,.json}
040e8d684abb1ca97e9aabd8f5a61e1a42c5653b  2593e721f6f9000d1c1a19f144236237dbad3b77d2380982baf030667eaf6f7c.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14
1aded004ab07f675042c03fe556744e47811831b  2593e721f6f9000d1c1a19f144236237dbad3b77d2380982baf030667eaf6f7c.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14.json
040e8d684abb1ca97e9aabd8f5a61e1a42c5653b  31f54e8b3a7628593ed122d67a426dbf6ba0687b3e406d753b61fc3e2d9e5014.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14
b3590a41726b003e3d15d997d52b1929f7608e02  31f54e8b3a7628593ed122d67a426dbf6ba0687b3e406d753b61fc3e2d9e5014.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14.json
```

We can see that the model files are identical but not the json as the json contains to different names where one is `facebook` and the other is `sshleifer`.

```
head \
	2593e721f6f9000d1c1a19f144236237dbad3b77d2380982baf030667eaf6f7c.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14.json \
	31f54e8b3a7628593ed122d67a426dbf6ba0687b3e406d753b61fc3e2d9e5014.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14.json

==> 2593e721f6f9000d1c1a19f144236237dbad3b77d2380982baf030667eaf6f7c.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14.json <==
{"url": "https://cdn.huggingface.co/facebook/mbart-large-cc25/pytorch_model.bin", "etag": "\"77a6a0d3b317fe29dc30de34840c519c-292\""}

==> 31f54e8b3a7628593ed122d67a426dbf6ba0687b3e406d753b61fc3e2d9e5014.2ed9a0461de33053de7171857e42bb9dd55d8722bb567aeaebff33a2a974fb14.json <==
{"url": "https://cdn.huggingface.co/sshleifer/mbart-large-cc25/pytorch_model.bin", "etag": "\"77a6a0d3b317fe29dc30de34840c519c-292\""}
```<|||||>Yes they're identical. Use facebook/ . It seems you fixed your issue?<|||||>I see the same error: Model name 'facebook/mbart-large-cc25' was not found in tokenizers model name list (facebook/mbart-large-en-ro, sshleifer/mbart-large-cc25) 
`tokenizer = MBartTokenizer.from_pretrained("facebook/mbart-large-cc25")` 
It works with mbart-large-en-ro<|||||>``python
tokenizer = MBartTokenizer.from_pretrained("facebook/mbart-large-cc25")
```
works for me on master<|||||>> 
> 
> ``python
> tokenizer = MBartTokenizer.from_pretrained("facebook/mbart-large-cc25")
> 
> ```
> works for me on master
> ```

Thanks. So, code is not released yet. Was using transformer 3.0.2 but installing from source works.