NPM fails installing zmq on OSX 10.9.5 - node.js

Question

I'm getting this error:
/bin/sh: pkg-config: command not found
gyp: Call to 'pkg-config libzmq --libs' returned exit status 127. while trying to load binding.gyp
I've tried upgrading nodejs to 5.1.0.
I've tried downgrading nodejs to 4.2.2.
I've tried completely removing nodejs manually then re-installing 4.2.2 and trying again.
I've tried the removal script here:
https://gist.github.com/brock/5b1b70590e1171c4ab54
Then re-installing each version and trying again.
I've tried downgrading to zeromq 4.0.7.
No luck.
Here's the complete error:
localhost:~ user$ npm install zmq
/
> zmq#2.14.0 install /Users/user/node_modules/zmq
> node-gyp rebuild
/bin/sh: pkg-config: command not found
gyp: Call to 'pkg-config libzmq --libs' returned exit status 127. while trying to load binding.gyp
gyp ERR! configure error
gyp ERR! stack Error: `gyp` failed with exit code: 1
gyp ERR! stack at ChildProcess.onCpExit (/usr/local/lib/node_modules/npm/node_modules/node-gyp/lib/configure.js:355:16)
gyp ERR! stack at emitTwo (events.js:87:13)
gyp ERR! stack at ChildProcess.emit (events.js:172:7)
gyp ERR! stack at Process.ChildProcess._handle.onexit (internal/child_process.js:200:12)
gyp ERR! System Darwin 13.4.0
gyp ERR! command "/usr/local/bin/node" "/usr/local/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "rebuild"
gyp ERR! cwd /Users/user/node_modules/zmq
gyp ERR! node -v v4.2.2
gyp ERR! node-gyp -v v3.0.3
gyp ERR! not ok
npm ERR! Darwin 13.4.0
npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "install" "zmq"
npm ERR! node v4.2.2
npm ERR! npm v2.14.7
npm ERR! code ELIFECYCLE
npm ERR! zmq#2.14.0 install: `node-gyp rebuild`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the zmq#2.14.0 install script 'node-gyp rebuild'.
npm ERR! This is most likely a problem with the zmq package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR! node-gyp rebuild
npm ERR! You can get their info via:
npm ERR! npm owner ls zmq
npm ERR! There is likely additional logging output above.
npm ERR! Please include the following file with any support request:
npm ERR! /Users/user/npm-debug.log

Answer 1

Here's what worked...
install zmq using brew : brew install zmq
export PKG_CONFIG_PATH=/usr/local/Cellar/zeromq/4.0.4/lib/pkgconfig/
sudo visudo
add the line Defaults env_keep += "PKG_CONFIG_PATH"
sudo npm install zmq

Answer 2

Here is how I fixed it:
Step 1:
brew install zmq
Step 2:
export PKG_CONFIG_PATH=/usr/local/Cellar/zeromq/4.2.5/lib/pkgconfig/
(Note: zeromq Version 4.2.5 in path above will need to be changed to whatever version you installed)
Step 3:
sudo visudo
and add
Defaults env_keep += "PKG_CONFIG_PATH"
Step 4:
In package.json > dependencies, add:
"zmq": "^2.15.3"
Step 5:
Run yarn or npm install