sphinx not able to find sphinx_rtd_theme
Ok...WTF...I have no idea how it works,
But I ran 

brew remove sphinx-doc

and "make html" worked,
If anyone can answer why and how this happened, please let me know...
I'm newbe of Sphinx,
I tried to use html_theme = 'sphinx_rtd_theme' in conf.py
but I get message below when I run "make html" :

sphinx_rtd_theme is no longer a hard dependency since version 1.4.0. Please install it manually.(pip install sphinx_rtd_theme)

I already installed it with pip install sphinx_rtd_them 
(part of pip list)

Package                  Version 

alabaster                0.7.11 
  sphinx-rtd-theme         0.4.1 
  Sphinx                   1.8.1  

Also I installed sphinx-doc with brew.
Anybody with same issue?? 
Another things to know is...My ubuntu PC works perfectly,
 but not works on Macbook pro...