Title: Unable to download cnn_dailymail dataset
State: closed
Labels: description: A bug in a dataset script provided in the library
name: dataset bug

### Script to reproduce the error
```
from datasets import load_dataset

train_dataset = load_dataset("cnn_dailymail", "3.0.0", split= 'train[:10%')
valid_dataset = load_dataset("cnn_dailymail","3.0.0", split="validation[:5%]")
```


### Error
```
---------------------------------------------------------------------------
NotADirectoryError                        Traceback (most recent call last)
<ipython-input-8-47c39c228935> in <module>()
      1 from datasets import load_dataset
      2 
----> 3 train_dataset = load_dataset("cnn_dailymail", "3.0.0", split= 'train[:10%')
      4 valid_dataset = load_dataset("cnn_dailymail","3.0.0", split="validation[:5%]")

5 frames
/usr/local/lib/python3.6/dist-packages/datasets/load.py in load_dataset(path, name, data_dir, data_files, split, cache_dir, features, download_config, download_mode, ignore_verifications, save_infos, script_version, **config_kwargs)
    609         download_config=download_config,
    610         download_mode=download_mode,
--> 611         ignore_verifications=ignore_verifications,
    612     )
    613 

/usr/local/lib/python3.6/dist-packages/datasets/builder.py in download_and_prepare(self, download_config, download_mode, ignore_verifications, try_from_hf_gcs, dl_manager, **download_and_prepare_kwargs)
    469                     if not downloaded_from_gcs:
    470                         self._download_and_prepare(
--> 471                             dl_manager=dl_manager, verify_infos=verify_infos, **download_and_prepare_kwargs
    472                         )
    473                     # Sync info

/usr/local/lib/python3.6/dist-packages/datasets/builder.py in _download_and_prepare(self, dl_manager, verify_infos, **prepare_split_kwargs)
    524         split_dict = SplitDict(dataset_name=self.name)
    525         split_generators_kwargs = self._make_split_generators_kwargs(prepare_split_kwargs)
--> 526         split_generators = self._split_generators(dl_manager, **split_generators_kwargs)
    527 
    528         # Checksums verification

/root/.cache/huggingface/modules/datasets_modules/datasets/cnn_dailymail/0128610a44e10f25b4af6689441c72af86205282d26399642f7db38fa7535602/cnn_dailymail.py in _split_generators(self, dl_manager)
    252     def _split_generators(self, dl_manager):
    253         dl_paths = dl_manager.download_and_extract(_DL_URLS)
--> 254         train_files = _subset_filenames(dl_paths, datasets.Split.TRAIN)
    255         # Generate shared vocabulary
    256 

/root/.cache/huggingface/modules/datasets_modules/datasets/cnn_dailymail/0128610a44e10f25b4af6689441c72af86205282d26399642f7db38fa7535602/cnn_dailymail.py in _subset_filenames(dl_paths, split)
    153     else:
    154         logging.fatal("Unsupported split: %s", split)
--> 155     cnn = _find_files(dl_paths, "cnn", urls)
    156     dm = _find_files(dl_paths, "dm", urls)
    157     return cnn + dm

/root/.cache/huggingface/modules/datasets_modules/datasets/cnn_dailymail/0128610a44e10f25b4af6689441c72af86205282d26399642f7db38fa7535602/cnn_dailymail.py in _find_files(dl_paths, publisher, url_dict)
    132     else:
    133         logging.fatal("Unsupported publisher: %s", publisher)
--> 134     files = sorted(os.listdir(top_dir))
    135 
    136     ret_files = []

NotADirectoryError: [Errno 20] Not a directory: '/root/.cache/huggingface/datasets/downloads/1bc05d24fa6dda2468e83a73cf6dc207226e01e3c48a507ea716dc0421da583b/cnn/stories'

```

Thanks for any suggestions.

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