Install pygraphviz on mountain lion

So you are trying to install pygraphviz on OSX and you get this:
$pip install pygraphviz
Traceback (most recent call last):

  File "<string>", line 16, in <module>

  File "/Users/grillermo/.virtualenvs/bandtastic/build/pygraphviz/setup.py", line 89, in <module>

    raise OSError,"Error locating graphviz."

OSError: Error locating graphviz.

Don´t worry you can install graphviz with Brew(you are already using brew arent you?)
like this:
brew install graphviz
But you now have to add an extra enviromental variable for the pip installer, all you have to do after brew is done is:
export PKG_CONFIG_PATH=/usr/local/Cellar/graphviz/2.28.0/lib/pkgconfig

And voilá, pip installer will run without problems.
You might be wondering why we exported that dir and not other, because thats where the file libcgraph.pc is located.