Exception:
Traceback (most recent call last):
File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/basecommand.py", line 215, in main
status = self.run(options, args)
File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/commands/install.py", line 342, in run
prefix=options.prefix_path,
File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/req/req_set.py", line 778, in install
requirement.uninstall(auto_confirm=True)
File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/req/req_install.py", line 754, in uninstall
paths_to_remove.remove(auto_confirm)
File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/req/req_uninstall.py", line 115, in remove
renames(path, new_path)
File "/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/pip/utils/__init__.py", line 267, in renames
shutil.move(old, new)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 300, in move
rmtree(src)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 247, in rmtree
rmtree(fullname, ignore_errors, onerror)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 252, in rmtree
onerror(os.remove, fullname, sys.exc_info())
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 250, in rmtree
os.remove(fullname)
OSError: [Errno 13] Permission denied: '/Library/Python/2.7/site-packages/pip-9.0.1-py2.7.egg/EGG-INFO/PKG-INFO'
You are using pip version 9.0.1, however version 19.1.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
在Mac下使用pip更新一个Python库时提示pip版本过低，底部命令行中显示需要升级，升级命令为：You should consider upgrading via the 'pip install --upgrade pip' command.
安装给出的命令输入：pip install --upgrade pip；结果执行后，还是报同样的错误。
重试N次后，发现还是执行失败。
最后上网查找后，才发现是权限问题，修改执行命令为：sudo pip install --upgrade pip
结果执行成功啦，普天同庆哦~