「Terminal」:pip报错'unkown-encoding'

C:\Users\本阿信>pip --version
Traceback (most recent call last):
  File "c:\python27\lib\runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "c:\python27\lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\Python27\Scripts\pip.exe\__main__.py", line 4, in <module>
  File "c:\python27\lib\site-packages\pip\_internal\cli\main.py", line 10, in <module>
    from pip._internal.cli.autocompletion import autocomplete
  File "c:\python27\lib\site-packages\pip\_internal\cli\autocompletion.py", line 9, in <module>
    from pip._internal.cli.main_parser import create_main_parser
  File "c:\python27\lib\site-packages\pip\_internal\cli\main_parser.py", line 7, in <module>
    from pip._internal.cli import cmdoptions
  File "c:\python27\lib\site-packages\pip\_internal\cli\cmdoptions.py", line 31, in <module>
    from pip._internal.utils.ui import BAR_TYPES
  File "c:\python27\lib\site-packages\pip\_internal\utils\ui.py", line 64, in <module>
    _BaseBar = _select_progress_class(IncrementalBar, Bar)  # type: Any
  File "c:\python27\lib\site-packages\pip\_internal\utils\ui.py", line 57, in _select_progress_class
    six.text_type().join(characters).encode(encoding)
LookupError: unknown encoding: cp65001

C:\Users\本阿信>set PYTHONIOENCODING=UTF-8

C:\Users\本阿信>pip --version
pip 20.0.2 from c:\python27\lib\site-packages\pip (python 2.7)