Grunt need compass installed in system PATH Warning

The warning seems to say it all.

1. If you're on OS X or Linux you probably already have Ruby installed; test with ruby -v in your terminal. When you've confirmed you have Ruby installed, run gem update --system && gem install compass to install Compass and Sass.

2. If that doesn't help, then install the grunt-contrib-compass package with the instructions at https://github.com/gruntjs/grunt-contrib-compass

I struggled for hours with this same error message when running a gulp watch, and despite installing, reinstalling, rebooting, it would still show up.

Got it working by uninstalling all my packages :

sudo gem uninstall bundler bundle compass sass compass-core compass-import-once

And installing bundle only

sudo gem install bundle bundler

And then run the command that magically installed everything I needed :

$ bundleFetching gem metadata from https://rubygems.org/...........Fetching version metadata from https://rubygems.org/..Installing sass 3.4.9Installing sassy-maps 0.4.0Installing breakpoint 2.5.0Installing hitimes 1.2.2Installing timers 4.0.1Installing celluloid 0.16.0Using chunky_png 1.3.3Using multi_json 1.10.1Installing compass-core 1.0.1Using compass-import-once 1.0.5Using rb-fsevent 0.9.4Using ffi 1.9.6Using rb-inotify 0.9.5Installing compass 1.0.1Installing json 1.8.1Installing listen 2.8.3Installing thor 0.19.1Installing fontcustom 1.3.7Installing modular-scale 2.0.5Installing normalize-scss 3.0.2Installing sass-css-importer 1.0.0.beta.0Installing sassy-buttons 0.2.6Installing susy 2.1.3Using bundler 1.8.0Bundle complete! 9 Gemfile dependencies, 24 gems now installed.Use `bundle show [gemname]` to see where a bundled gem is installed.Post-install message from compass:    Compass is charityware. If you love it, please donate on our behalf at http://umdf.org/compass Thanks!Post-install message from fontcustom:>> Thanks for installing Font Custom! Please ensure that fontforge is installed before compiling any icons. Visit <http://fontcustom.com> for instructions.

Now, don't ask me why, but it all works :-)

Hope that can help anybody out there, I really struggled on this one ...

Just need to write on console -> (or sudo )gem install compass ,because the npm command wouldn´t do anything