title: tarfile can't open tgz
body: <p>I am trying to download tgz file from this website:
  <a href="https://plg.uwaterloo.ca/cgi-bin/cgiwrap/gvcormac/foo07" rel="nofollow noreferrer">https://plg.uwaterloo.ca/cgi-bin/cgiwrap/gvcormac/foo07</a></p>
  
  <p>here is my script:</p>
  
  <pre><code>import os
  from six.moves import urllib
  import tarfile
  
  spam_path=os.path.join('ML', 'spam')
  root_download='https://plg.uwaterloo.ca/cgi-bin/cgiwrap/gvcormac/foo07'
  spam_url=root_download+'255 MB Corpus (trec07p.tgz)'
  
  if not os.path.isdir(spam_path):
      os.makedirs(spam_path)
  
  path=os.path.join(spam_path, 'trec07p.tgz')
  if not os.path.isfile('trec07p.tgz'):
      urllib.request.urlretrieve(spam_url,path)
  tar_file=tarfile.open(path)
  </code></pre>
  
  <p>I am not sure what I am missing but the following error is returned:</p>
  
  <pre><code>---------------------------------------------------------------------------
  ReadError                                 Traceback (most recent call last)
  &lt;ipython-input-21-5644813e0670&gt; in &lt;module&gt;()
       18 if not os.path.isfile('trec07p.tgz'):
       19     urllib.request.urlretrieve(spam_url,path)
  ---&gt; 20 tar_file=tarfile.open(path)
       21 # tar_file.extractall(path)
       22 # tar_file.close()
  
  /anaconda/lib/python2.7/tarfile.pyc in open(cls, name, mode, fileobj, bufsize, **kwargs)
     1678                         fileobj.seek(saved_pos)
     1679                     continue
  -&gt; 1680             raise ReadError("file could not be opened successfully")
     1681 
     1682         elif ":" in mode:
  
  ReadError: file could not be opened successfully
  </code></pre>
  
  <p>Thank you in advance for your help!</p>