代码：
newsgroups_train = fetch_20newsgroups(subset='train')
错误：
Traceback (most recent call last):
File "create_tsv.py", line 10, in <module>
newsgroups_train = fetch_20newsgroups(subset='train')
File "/usr/lib/python2.7/dist-packages/sklearn/datasets/twenty_newsgroups.py", line 207, in fetch_20newsgroups
cache_path=cache_path)
File "/usr/lib/python2.7/dist-packages/sklearn/datasets/twenty_newsgroups.py", line 89, in download_20newsgroups
tarfile.open(archive_path, "r:gz").extractall(path=target_dir)
File "/usr/lib/python2.7/tarfile.py", line 1678, in open
return func(name, filemode, fileobj, **kwargs)
File "/usr/lib/python2.7/tarfile.py", line 1727, in gzopen
**kwargs)
File "/usr/lib/python2.7/tarfile.py", line 1705, in taropen
return cls(name, mode, fileobj, **kwargs)
File "/usr/lib/python2.7/tarfile.py", line 1574, in __init__
self.firstmember = self.next()
File "/usr/lib/python2.7/tarfile.py", line 2338, in next
raise ReadError("empty file")
tarfile.ReadError: empty file