pip was broken after upgrade to 21

[ninjachen]

pip version

21.0.1

Python version

2.7

OS

macos

Additional information

No response

Description

I upgrade pip from 6.1.1 to 21.0.1, then it was not working.

Expected behavior

Expect pip install works

How to Reproduce

1. sudo pip install -U pip
2. pip
3. Failed with error message

 Traceback (most recent call last):
  File "/usr/local/bin/pip", line 9, in <module>
    load_entry_point('pip==21.0.1', 'console_scripts', 'pip')()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources/__init__.py", line 565, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources/__init__.py", line 2697, in load_entry_point
    return ep.load()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources/__init__.py", line 2370, in load
    return self.resolve()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources/__init__.py", line 2376, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/Library/Python/2.7/site-packages/pip/_internal/cli/main.py", line 60
    sys.stderr.write(f"ERROR: {exc}")
                                   ^
SyntaxError: invalid syntax

**Output**

```console

```


**Code of Conduct**

- [X] I agree to follow the PSF Code of Conduct

[ninjachen]

Here is a snapshot of the error

[ninjachen]

To someone meet the same issue, I have a workaround

sudo rm -rf  /Library/Python/2.7/site-packages/pip*
sudo python -m ensurepip
sudo pip install --upgrade pip==18.1

This should work on maxOS

[uranusjr]

Python 2 is no longer supported. 20.3.4 is the last version taht does.