Issue: Dataset download error
Hi, thanks for the answer. 

I gave a try to the problem today. But I encountered an upload error: 

```
git push -u origin fix_link_iwslt
Enter passphrase for key '/home2/xuhuizh/.ssh/id_rsa': 
ERROR: Permission to huggingface/datasets.git denied to XuhuiZhou.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
```

Any insight here? 

By the way, when I run the datasets-cli command, it shows the following error, but does not seem to be the error coming from `iwslt.py`

```
Traceback (most recent call last):
  File "/home2/xuhuizh/anaconda3/envs/UMT/bin/datasets-cli", line 33, in <module>
    sys.exit(load_entry_point('datasets', 'console_scripts', 'datasets-cli')())
  File "/home2/xuhuizh/projects/datasets/src/datasets/commands/datasets_cli.py", line 35, in main
    service.run()
  File "/home2/xuhuizh/projects/datasets/src/datasets/commands/test.py", line 141, in run
    try_from_hf_gcs=False,
  File "/home2/xuhuizh/projects/datasets/src/datasets/builder.py", line 579, in download_and_prepare
    dl_manager=dl_manager, verify_infos=verify_infos, **download_and_prepare_kwargs
  File "/home2/xuhuizh/projects/datasets/src/datasets/builder.py", line 639, in _download_and_prepare
    self.info.download_checksums, dl_manager.get_recorded_sizes_checksums(), "dataset source files"
  File "/home2/xuhuizh/projects/datasets/src/datasets/utils/info_utils.py", line 32, in verify_checksums
    raise ExpectedMoreDownloadedFiles(str(set(expected_checksums) - set(recorded_checksums)))
datasets.utils.info_utils.ExpectedMoreDownloadedFiles: {'https://wit3.fbk.eu/archive/2017-01-trnmted//texts/DeEnItNlRo/DeEnItNlRo/DeEnItNlRo-DeEnItNlRo.tgz'}
```
The download link in `iwslt2017.py` file does not seem to work anymore.

For example, `FileNotFoundError: Couldn't find file at https://wit3.fbk.eu/archive/2017-01-trnted/texts/zh/en/zh-en.tgz`

Would be nice if we could modify it script and use the new downloadable link?
Issue: Dataset download error 
 The download link in `iwslt2017.py` file does not seem to work anymore.

For example, `FileNotFoundError: Couldn't find file at https://wit3.fbk.eu/archive/2017-01-trnted/texts/zh/en/zh-en.tgz`

Would be nice if we could modify it script and use the new downloadable link? 
 Hi, thanks for the answer. 

I gave a try to the problem today. But I encountered an upload error: 

```
git push -u origin fix_link_iwslt
Enter passphrase for key '/home2/xuhuizh/.ssh/id_rsa': 
ERROR: Permission to huggingface/datasets.git denied to XuhuiZhou.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
```

Any insight here? 

By the way, when I run the datasets-cli command, it shows the following error, but does not seem to be the error coming from `iwslt.py`

```
Traceback (most recent call last):
  File "/home2/xuhuizh/anaconda3/envs/UMT/bin/datasets-cli", line 33, in <module>
    sys.exit(load_entry_point('datasets', 'console_scripts', 'datasets-cli')())
  File "/home2/xuhuizh/projects/datasets/src/datasets/commands/datasets_cli.py", line 35, in main
    service.run()
  File "/home2/xuhuizh/projects/datasets/src/datasets/commands/test.py", line 141, in run
    try_from_hf_gcs=False,
  File "/home2/xuhuizh/projects/datasets/src/datasets/builder.py", line 579, in download_and_prepare
    dl_manager=dl_manager, verify_infos=verify_infos, **download_and_prepare_kwargs
  File "/home2/xuhuizh/projects/datasets/src/datasets/builder.py", line 639, in _download_and_prepare
    self.info.download_checksums, dl_manager.get_recorded_sizes_checksums(), "dataset source files"
  File "/home2/xuhuizh/projects/datasets/src/datasets/utils/info_utils.py", line 32, in verify_checksums
    raise ExpectedMoreDownloadedFiles(str(set(expected_checksums) - set(recorded_checksums)))
datasets.utils.info_utils.ExpectedMoreDownloadedFiles: {'https://wit3.fbk.eu/archive/2017-01-trnmted//texts/DeEnItNlRo/DeEnItNlRo/DeEnItNlRo-DeEnItNlRo.tgz'}
```