title: Failed to install pip for pypy on Ubuntu
body: <p>I cannot install pip for pypy 4.0.1 on Ubuntu 15.10. </p>
  
  <p>I downloaded pypy 4.0.1 from <a href="http://pypy.org/download.html" rel="noreferrer">http://pypy.org/download.html</a>. Created a symlink for it. And used wget to download get-pip.py from <a href="https://bootstrap.pypa.io/get-pip.py" rel="noreferrer">https://bootstrap.pypa.io/get-pip.py</a>. </p>
  
  <p>But when I ran <code>sudo pypy get-pip.py</code>, I got exception:</p>
  
  <pre><code>Collecting pip
  Exception:
  Traceback (most recent call last):
      File "/tmp/tmps2kjCI/pip.zip/pip/basecommand.py", line 211, in main
        status = self.run(options, args)
      File "/tmp/tmps2kjCI/pip.zip/pip/commands/install.py", line 294, in run
        requirement_set.prepare_files(finder)
      File "/tmp/tmps2kjCI/pip.zip/pip/req/req_set.py", line 334, in prepare_files
        functools.partial(self._prepare_file, finder))
      File "/tmp/tmps2kjCI/pip.zip/pip/req/req_set.py", line 321, in _walk_req_to_install
        more_reqs = handler(req_to_install)
      File "/opt/pypy-4.0.1-linux64/lib_pypy/_functools.py", line 42, in __call__
        return self._func(*(self._args + fargs), **fkeywords)
      File "/tmp/tmps2kjCI/pip.zip/pip/req/req_set.py", line 491, in _prepare_file
        session=self.session)
      File "/tmp/tmps2kjCI/pip.zip/pip/download.py", line 825, in unpack_url
        session,
      File "/tmp/tmps2kjCI/pip.zip/pip/download.py", line 673, in unpack_http_url
        from_path, content_type = _download_http_url(link, session, temp_dir)
      File "/tmp/tmps2kjCI/pip.zip/pip/download.py", line 885, in _download_http_url
        with open(file_path, 'wb') as content_file:
      TypeError: expected string, got NoneType object
  </code></pre>
  
  <p>I could run <code>sudo python get-pip.py</code> without problem but failed with pypy. I also tried Ubuntu 12.04 and 14.04 but no luck. </p>
  
  <p>I have Python 2.7.10 installed and I'm using a Linode machine. But changed to a DigitalOcean one didn't help. </p>