Resolved 'rosgraph' dependency issue by adding python-netifaces pip

While trying to do a brew install of groovy, I kept encountering the following error:

>ERROR: the following packages/stacks could not have their rosdep keys resolved
>to system dependencies:
>rosgraph: No definition of [python-netifaces] for OS [osx]

I went ahead and added the definition for python-netifaces.  It exists as a pip called 'netifaces'.