pip: pip install --upgrade without permissions deletes old pip before failing

• Pip version: 8.1-1
• Python version: 2.7.11
• Operating System: 10.9.5

Description:

Running pip install --upgrade pip, without proper permissions, results in:

1. Old pip getting uninstalled
2. New pip failing to install due to permissions issues when writing files

Now the system lacks pip entirely.

What I’ve run:

I have pip installed with homebrew, but forgot about this. I ran:

pip install --upgrade pip

Got back:

Collecting pip
  Downloading pip-8.1.2-py2.py3-none-any.whl (1.2MB)
    100% |████████████████████████████████| 1.2MB 270kB/s
Installing collected packages: pip
  Found existing installation: pip 8.1.1
    Uninstalling pip-8.1.1:
Exception:
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/pip/basecommand.py", line 209, in main
    status = self.run(options, args)
  File "/usr/local/lib/python2.7/site-packages/pip/commands/install.py", line 317, in run
    prefix=options.prefix_path,
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_set.py", line 726, in install
    requirement.uninstall(auto_confirm=True)
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_install.py", line 746, in uninstall
    paths_to_remove.remove(auto_confirm)
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_uninstall.py", line 115, in remove
    renames(path, new_path)
  File "/usr/local/lib/python2.7/site-packages/pip/utils/__init__.py", line 267, in renames
    shutil.move(old, new)
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 303, in move
    os.unlink(src)
OSError: [Errno 13] Permission denied: '/usr/local/lib/python2.7/site-packages/pip-8.1.1.dist-info/DESCRIPTION.rst'
You are using pip version 8.1.1, however version 8.1.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

Then I ran:

sudo pip install --upgrade pip

And got back:

sudo: pip: command not found