The problem is with a new 'protection' in OS X 'el capitan' which breaks the pip update, this is not restricted to Ansible but to any pip package you install with sudo.
https://github.com/ansible/ansible/issues/13820 -- Brian Coca -- You received this message because you are subscribed to the Google Groups "Ansible Project" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/ansible-project/CAJ5XC8kK64NgomMDpoz8Dw6LrbstMh%2BSrTpjZQd_nrUK6%2Bqktw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
