Failing at collected packages, Exceptions, OSError 13 (El Capitan)

Following a good suggestion earlier to uninstall and reinstall homebrew, I also updated my Python version to 3.5.1. Running this:
$ ./letsencrypt-auto --debug --version
I got through Bootstrapping dependencies… Using Homebrew… (two warnings that augeas-1.4.0 and dialog-1.3* were already installed) then came the Exceptions:

pip not installed
Installing pip...
Collecting pip
  Using cached pip-8.1.1-py2.py3-none-any.whl
Collecting wheel
  Using cached wheel-0.29.0-py2.py3-none-any.whl
Installing collected packages: pip, wheel
Traceback (most recent call last):
  File "/var/folders/__/6sqb0**/T/tmp6UeWY5/", line 209, in main
    status =, args)
  File "/var/folders/__/6sqb0**/T/tmp6UeWY5/", line 317, in run
  File "/var/folders/__/6sqb0**/T/tmp6UeWY5/", line 732, in install
  File "/var/folders/__/6sqb0**/T/tmp6UeWY5/", line 835, in install
    self.move_wheel_files(self.source_dir, root=root, prefix=prefix)
  File "/var/folders/__/6sqb0**/T/tmp6UeWY5/", line 1030, in move_wheel_files
  File "/var/folders/__/6sqb0**/T/tmp6UeWY5/", line 344, in move_wheel_files
    clobber(source, lib_dir, True)
  File "/var/folders/__/6sqb0**/T/tmp6UeWY5/", line 315, in clobber
  File "/var/folders/__/6sqb0**/T/tmp6UeWY5/", line 83, in ensure_dir
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/", line 157, in makedirs
    mkdir(name, mode)
OSError: [Errno 13] Permission denied: '/Library/Python/2.7/site-packages/pip'

Permissions on python - owner is root on this Mac mini. Newbie question: do I need to uninstall and reinstall python 2.7.11 for this to work? Apparently Python 3.x installed in somewhere other than /Library/Python so I’m unclear on best path forward.


Update: used brew to install python (instead of download/install), which installed pip too.
Install success: lets encrypt 0.5.0