Removing all package packages installed at the system level?

When I started learning Python I didn't know about virtualenv and so I installed all my stuff at the system level.

I wanted to do a full cleanup to prevent problems. However, creating a requirements .txt file and then trying to run uninstall, it throws the following error and does not complete the uninstall. Any ideas what could be wrong?

> Exception:
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/pip/basecommand.py", line 215, in main
    status = self.run(options, args)
  File "/usr/local/lib/python2.7/site-packages/pip/commands/uninstall.py", line 76, in run
    requirement_set.uninstall(auto_confirm=options.yes)
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_set.py", line 346, in uninstall
    req.uninstall(auto_confirm=auto_confirm)
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_install.py", line 754, 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/2.7.12_2/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/awscli-1.11.83.dist-info/DESCRIPTION.rst'