Ansible: can't `make webdocs`.

ansible_make-webdocs--error.log

devel ⎋ uname -a
Darwin titan.local 15.6.0 Darwin Kernel Version 15.6.0: Thu Jun 23 18:25:34 PDT 2016; root:xnu-3248.60.10~1/RELEASE_X86_64 x86_64
devel ⎋ ls
CHANGELOG.md             Makefile                 ansible-core-sitemap.xml docsite                  setup.py
CODING_GUIDELINES.md     README.md                bin                      examples                 shippable.yml
CONTRIBUTING.md          RELEASES.txt             contrib                  hacking                  test
COPYING                  ROADMAP.rst              docs                     lib                      ticket_stubs
MANIFEST.in              VERSION                  docs-api                 packaging                tox.ini
devel ⎋ git show --name-status
commit 67177105e3c1bc0b0d44c58155c56ae0e4d6fdb2
Author: Toshio Kuratomi <a.badger@gmail.com>
Date:   Fri Sep 2 08:27:01 2016 -0700

    We now have an exception return value.  Make use of it instead of putting the traceback into msg (#17365)

M       lib/ansible/module_utils/basic.py
devel ⎋ pwd
/Users/olistik/projects/_docs/ansible
devel ⎋ python --version
Python 3.4.3
devel ⎋ pyenv --version
pyenv 1.0.0
devel ⎋ make webdocs
(cd docsite/; make docs)
rm -rf htmlout
rm -f .buildinfo
rm -f *.inv
rm -rf *.doctrees
Cleaning up minified css files
find . -type f -name "*.min.css" -delete
Cleaning up byte compiled python stuff
find . -regex ".*\.py[co]$" -delete
Cleaning up editor backup files
find . -type f \( -name "*~" -or -name "#*" \) -delete
find . -type f \( -name "*.swp" \) -delete
Cleaning up generated rst
rm rst/list_of_*.rst
rm: rst/list_of_*.rst: No such file or directory
make[1]: [clean] Error 1 (ignored)
rm rst/*_by_category.rst
rm: rst/*_by_category.rst: No such file or directory
make[1]: [clean] Error 1 (ignored)
rm rst/*_module.rst
rm: rst/*_module.rst: No such file or directory
make[1]: [clean] Error 1 (ignored)
PYTHONPATH=../lib ../hacking/dump_playbook_attributes.py --template-dir=../hacking/templates --output-dir=rst/
Traceback (most recent call last):
  File "../hacking/dump_playbook_attributes.py", line 6, in <module>
    from ansible.playbook import  Play
  File "/Users/olistik/projects/_docs/ansible/lib/ansible/playbook/__init__.py", line 25, in <module>
    from ansible.playbook.play import Play
  File "/Users/olistik/projects/_docs/ansible/lib/ansible/playbook/play.py", line 27, in <module>
    from ansible.playbook.base import Base
  File "/Users/olistik/projects/_docs/ansible/lib/ansible/playbook/base.py", line 36, in <module>
    from ansible.parsing.dataloader import DataLoader
  File "/Users/olistik/projects/_docs/ansible/lib/ansible/parsing/dataloader.py", line 27, in <module>
    from yaml import YAMLError
ImportError: No module named 'yaml'
make[1]: *** [directives] Error 1
make: *** [webdocs] Error 2