Collecting selenium
  Using cached selenium-2.53.6-py2.py3-none-any.whl
Installing collected packages: selenium
  Found existing installation: selenium 2.51.1
    Uninstalling selenium-2.51.1:
Exception:
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/pip-8.1.1-py2.7.egg/pip/basecommand.py", line 209, in main
    status = self.run(options, args)
  File "/Library/Python/2.7/site-packages/pip-8.1.1-py2.7.egg/pip/commands/install.py", line 317, in run
    prefix=options.prefix_path,
  File "/Library/Python/2.7/site-packages/pip-8.1.1-py2.7.egg/pip/req/req_set.py", line 726, in install
    requirement.uninstall(auto_confirm=True)
  File "/Library/Python/2.7/site-packages/pip-8.1.1-py2.7.egg/pip/req/req_install.py", line 746, in uninstall
    paths_to_remove.remove(auto_confirm)
  File "/Library/Python/2.7/site-packages/pip-8.1.1-py2.7.egg/pip/req/req_uninstall.py", line 115, in remove
    renames(path, new_path)
  File "/Library/Python/2.7/site-packages/pip-8.1.1-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/selenium-2.51.1-py2.7.egg/EGG-INFO/dependency_links.txt'
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.