title: I can't install any package using pip
body: <p>Recently I installed Python 2.7 as I wanted to rewrite some script written in Python 3.5. After I modified the PATH environment variable I wanted to install pandas module I'm gettint the following error:</p>
  
  <pre><code>C:\Python27&gt;pip install pandas
  Collecting pandas
  Exception:
  Traceback (most recent call last):
    File "c:\python27\lib\site-packages\pip\basecommand.py", line 209, in main
      status = self.run(options, args)
    File "c:\python27\lib\site-packages\pip\commands\install.py", line 299, in run
  
      requirement_set.prepare_files(finder)
    File "c:\python27\lib\site-packages\pip\req\req_set.py", line 360, in prepare_
  files
      ignore_dependencies=self.ignore_dependencies))
    File "c:\python27\lib\site-packages\pip\req\req_set.py", line 512, in _prepare
  _file
      finder, self.upgrade, require_hashes)
    File "c:\python27\lib\site-packages\pip\req\req_install.py", line 273, in popu
  late_link
      self.link = finder.find_requirement(self, upgrade)
    File "c:\python27\lib\site-packages\pip\index.py", line 440, in find_requireme
  nt
      all_candidates = self.find_all_candidates(req.name)
    File "c:\python27\lib\site-packages\pip\index.py", line 398, in find_all_candi
  dates
      for page in self._get_pages(url_locations, project_name):
    File "c:\python27\lib\site-packages\pip\index.py", line 543, in _get_pages
      page = self._get_page(location)
    File "c:\python27\lib\site-packages\pip\index.py", line 646, in _get_page
      return HTMLPage.get_page(link, session=self.session)
    File "c:\python27\lib\site-packages\pip\index.py", line 755, in get_page
      "Cache-Control": "max-age=600",
    File "c:\python27\lib\site-packages\pip\_vendor\requests\sessions.py", line 48
  0, in get
      return self.request('GET', url, **kwargs)
    File "c:\python27\lib\site-packages\pip\download.py", line 378, in request
      return super(PipSession, self).request(method, url, *args, **kwargs)
    File "c:\python27\lib\site-packages\pip\_vendor\requests\sessions.py", line 46
  8, in request
      resp = self.send(prep, **send_kwargs)
    File "c:\python27\lib\site-packages\pip\_vendor\requests\sessions.py", line 60
  8, in send
      r.content
    File "c:\python27\lib\site-packages\pip\_vendor\requests\models.py", line 737,
   in content
      self._content = bytes().join(self.iter_content(CONTENT_CHUNK_SIZE)) or bytes
  ()
    File "c:\python27\lib\site-packages\pip\_vendor\requests\models.py", line 660,
   in generate
      for chunk in self.raw.stream(chunk_size, decode_content=True):
    File "c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\resp
  onse.py", line 344, in stream
      data = self.read(amt=amt, decode_content=decode_content)
    File "c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\resp
  onse.py", line 301, in read
      data = self._fp.read(amt)
    File "c:\python27\lib\site-packages\pip\_vendor\cachecontrol\filewrapper.py",
  line 54, in read
      self.__callback(self.__buf.getvalue())
    File "c:\python27\lib\site-packages\pip\_vendor\cachecontrol\controller.py", l
  ine 297, in cache_response
      self.serializer.dumps(request, response, body=body),
    File "c:\python27\lib\site-packages\pip\download.py", line 281, in set
      return super(SafeFileCache, self).set(*args, **kwargs)
    File "c:\python27\lib\site-packages\pip\_vendor\cachecontrol\caches\file_cache
  .py", line 99, in set
      with self.lock_class(name) as lock:
    File "c:\python27\lib\site-packages\pip\_vendor\lockfile\mkdirlockfile.py", li
  ne 19, in __init__
      LockBase.__init__(self, path, threaded, timeout)
    File "c:\python27\lib\site-packages\pip\_vendor\lockfile\__init__.py", line 24
  2, in __init__
      hash(self.path)))
    File "c:\python27\lib\ntpath.py", line 85, in join
      result_path = result_path + p_path
  UnicodeDecodeError: 'ascii' codec can't decode byte 0xb3 in position 5: ordinal
  not in range(128)
  </code></pre>
  
  <p>Any ideas how to overcome this problem? I deleted the paths to Python 3.5 but it didn't help.</p>
  
  <p>I also cannot install other packages.</p>