[igraph] Solution for installing python-igraph for Anaconda using Homebrew igraph [OS X]

[Christopher Cameron]

I wanted to share this solution with the list in case others run into this 
issue:

I ran into errors about libiconv.la and/or libxml2.2.dylib while trying to 
install python-igraph on a clean install of OS X 10.11, with homebrew installed 
igraph C library and Anaconda Python 2.7. I came across a few posts about 
possible solutions but wanted to offer an solution that does not involve 
renaming/moving system library files. The method below uses shell variables and 
extra pip flags to build python-igraph against the homebrew C library. 
Longer description and beautified commands here: 
http://chrisjcameron.github.io/2016/04/27/homebrew_and_anaconda/

Temporarily change your PATH to avoid anaconda directories (e.g.)
    % PATH=/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/X11/bin

Install homebrew iGraph normally: 
    % brew install igraph

Use extra flags so python-igraph is not built against the libraries bundled 
with Anaconda:
    % ~/anaconda/bin/pip install python-igraph --global-option=build_ext 
--global-option="-L/usr/lib:/usr/local/lib"

I was able to import igraph and run the igraph test suite successfully.