title: Python 3.5 pip 9 AttributeError: 'NoneType' object has no attribute 'bytes'
body: <p>What is the problem? I tried "<strong>python -m pip install -U pip</strong>" and "<strong>python -m pip install --upgrade pip</strong>" both with the same error (and "<strong>pip install -U  --force-reinstall pip</strong>"). what should I do?</p>
  
  <pre><code>C:\Users\Peyman\PycharmProjects\untitled3&gt;python -m pip install -U pip
  Collecting pip
    Using cached https://files.pythonhosted.org/packages/5f/25/e52d3f31441505a5f3af41213346e5b6c221c9e086a166f3703d2ddaf940/pip-18.0-py2.py3-none-any.whl
  Installing collected packages: pip
    Found existing installation: pip 9.0.3
      Uninstalling pip-9.0.3:
        Successfully uninstalled pip-9.0.3
    Rolling back uninstall of pip
  Exception:
  Traceback (most recent call last):
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\basecommand.py", line 215, in main
      status = self.run(options, args)
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\commands\install.py", line 342, in run
      prefix=options.prefix_path,
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\req\req_set.py", line 784, in install
      **kwargs
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\req\req_install.py", line 851, in install
      self.move_wheel_files(self.source_dir, root=root, prefix=prefix)
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\req\req_install.py", line 1064, in move_wheel_files
      isolated=self.isolated,
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\wheel.py", line 462, in move_wheel_files
      generated.extend(maker.make(spec))
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\_vendor\distlib\scripts.py", line 372, in make
      self._make_script(entry, filenames, options=options)
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\_vendor\distlib\scripts.py", line 276, in _make_script
      self._write_script(scriptnames, shebang, script, filenames, ext)
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\_vendor\distlib\scripts.py", line 212, in _write_script
      launcher = self._get_launcher('t')
    File "C:\Users\Peyman\AppData\Roaming\Python\Python35\site-packages\pip\_vendor\distlib\scripts.py", line 351, in _get_launcher
      result = finder(distlib_package).find(name).bytes
  AttributeError: 'NoneType' object has no attribute 'bytes'
  You are using pip version 9.0.3, however version 18.0 is available.
  You should consider upgrading via the 'python -m pip install --upgrade pip' command.
  </code></pre>