Trec Dataset Connection Error
Thanks for reporting.
That's because the download url has changed. The old url now redirects to the new one but we don't support redirection for downloads.

I'm opening a PR to update the url
**Datasets Version:**
1.1.2

**Python Version:**
3.6/3.7


**Code:**
```python
from datasets import load_dataset
load_dataset("trec")
```

**Expected behavior:**
Download Trec dataset and load Dataset object

**Current Behavior:**
Get a connection error saying it couldn't reach http://cogcomp.org/Data/QA/QC/train_5500.label (but the link doesn't seem broken)

<details>
  <summary>Error Logs</summary>
 

Using custom data configuration default
Downloading and preparing dataset trec/default (download: 350.79 KiB, generated: 403.39 KiB, post-processed: Unknown size, total: 754.18 KiB) to /root/.cache/huggingface/datasets/trec/default/1.1.0/ca4248481ad244f235f4cf277186cad2ee8769f975119a2bbfc41b8932b88bd7...
---------------------------------------------------------------------------
ConnectionError                           Traceback (most recent call last)
<ipython-input-8-66bf1242096e> in <module>()
----> 1 load_dataset("trec")

10 frames
/usr/local/lib/python3.6/dist-packages/datasets/utils/file_utils.py in get_from_cache(url, cache_dir, force_download, proxies, etag_timeout, resume_download, user_agent, local_files_only, use_etag)
    473         elif response is not None and response.status_code == 404:
    474             raise FileNotFoundError("Couldn't find file at {}".format(url))
--> 475         raise ConnectionError("Couldn't reach {}".format(url))
    476 
    477     # Try a second time

ConnectionError: Couldn't reach http://cogcomp.org/Data/QA/QC/train_5500.label

</details>