python pip 不能用报错: ImportError: No module named _internal

使用python　pip安装包的时候报错:
Traceback (most recent call last):
  File "/usr/local/bin/pip", line 7, in <module>
    from pip._internal import main
ImportError: No module named _internal

解决办法:
python3 -m pip install --upgrade pip

pip install --upgrade pip