Brew error: Could not symlink, path is not writable

As explained here by Rick:

Start with brew doctor which will show you errors with your brew setup.

You might see something like this: "Warning: /usr/local/lib/pkgconfig isn't writable."

It will give you the advice that: "You should probably chown /usr/local/lib/pkgconfig".

This means: sudo chown -R $(whoami) /usr/local/lib/pkgconfig

Then you will need to link the files with this: brew link yourLibrary

If this does not work hopefully the output of brew doctor will give you enough to continue the search.

http://stackoverflow.com/questions/27784545/brew-error-could-not-symlink-path-is-not-writable