title: “Unable to locate finder for 'pip._vendor.distlib'” error when using "pip install virtualenv"
body: <p>I am trying to install virtualenv with Python 3.6 version under Windows 10.When I run "pip install virtualenv" I'm getting this error. I am a newbie to Python.</p>
  
  <pre><code>Collecting virtualenv
    Downloading virtualenv-15.0.3-py2.py3-none-any.whl (3.5MB)
      100% |████████████████████████████████| 3.5MB 256kB/s
  Installing collected packages: virtualenv
  Exception:
  Traceback (most recent call last):
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\basecommand.py", line 215, in main
      status = self.run(options, args)
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\commands\install.py", line 317, in run
      prefix=options.prefix_path,
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\req\req_set.py", line 742, in install
      **kwargs
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\req\req_install.py", line 831, in install
      self.move_wheel_files(self.source_dir, root=root, prefix=prefix)
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\req\req_install.py", line 1032, in move_wheel_files
      isolated=self.isolated,
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\wheel.py", line 493, in move_wheel_files
      maker.make_multiple(['%s = %s' % kv for kv in console.items()])
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\_vendor\distlib\scripts.py", line 383, in make_multiple
      filenames.extend(self.make(specification, options))
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\_vendor\distlib\scripts.py", line 372, in make
      self._make_script(entry, filenames, options=options)
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\_vendor\distlib\scripts.py", line 276, in _make_script
      self._write_script(scriptnames, shebang, script, filenames, ext)
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\_vendor\distlib\scripts.py", line 212, in _write_script
      launcher = self._get_launcher('t')
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\_vendor\distlib\scripts.py", line 351, in _get_launcher
      result = finder(distlib_package).find(name).bytes
    File "c:\users\corey shaw\appdata\local\programs\python\python36\lib\site-packages\pip\_vendor\distlib\resources.py", line 324, in finder
      raise DistlibException('Unable to locate finder for %r' % package)
  pip._vendor.distlib.DistlibException: Unable to locate finder for 'pip._vendor.distlib'
  </code></pre>