title: pip throws TypeError: parse() got an unexpected keyword argument 'transport_encoding' when trying to install new packages
body: <p>I am using the latest version of Anaconda3. I just installed it and I am trying to download some packages. I am using the Anaconda Prompt. While trying to use pip to do anything (including upgrading existing packages) I get the following traceback.</p>
  
  <pre><code>    Exception:
  Traceback (most recent call last):
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\basecommand.py", line 215, in main
      status = self.run(options, args)
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\commands\install.py", line 335, in run
      wb.build(autobuilding=True)
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\wheel.py", line 749, in build
      self.requirement_set.prepare_files(self.finder)
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\req\req_set.py", line 380, in prepare_files
      ignore_dependencies=self.ignore_dependencies))
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\req\req_set.py", line 487, in _prepare_file
      req_to_install, finder)
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\req\req_set.py", line 428, in _check_skip_installed
      req_to_install, upgrade_allowed)
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\index.py", line 465, in find_requirement
      all_candidates = self.find_all_candidates(req.name)
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\index.py", line 423, in find_all_candidates
      for page in self._get_pages(url_locations, project_name):
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\index.py", line 568, in _get_pages
      page = self._get_page(location)
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\index.py", line 683, in _get_page
      return HTMLPage.get_page(link, session=self.session)
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\index.py", line 811, in get_page
      inst = cls(resp.content, resp.url, resp.headers)
    File "C:\Users\csprock\Anaconda3\lib\site-packages\pip\index.py", line 731, in __init__
      namespaceHTMLElements=False,
  TypeError: parse() got an unexpected keyword argument 'transport_encoding'
  </code></pre>
  
  <p>Any ideas? (this problem only started after I installed tensorflow) Thanks. </p>