brew install grafana/grafana/grafana fails with error

[zhenglaizhang]

First of all, thanks for the great work on the project, it's really cool!
I tried to install the grafana, but failed with following errors:

➜  ~ brew install grafana/grafana/grafana
==> Installing grafana from grafana/grafana
==> Downloading https://github.com/grafana/grafana/archive/v3.0-beta5.tar.gz
Already downloaded: /Library/Caches/Homebrew/grafana-3.0-beta5.tar.gz
Warning: tried to stage empty resources array
==> go run build.go setup
==> go run build.go build
==> npm install
==> npm install grunt-cli
==> node_modules/grunt-cli/bin/grunt build
Last 15 lines from /Users/BX/Library/Logs/Homebrew/grafana/05.grunt:
Running "concat:cssFonts" (concat) task
File public_gen/css/fonts.min.css created.

Running "styleguide" task

Running "sasslint:target" (sasslint) task

public/sass/components/_dropdown.scss
  70:1  error  Please check validity of the block starting from line #70  Fatal

✖ 1 problem (1 error, 0 warnings)

Warning:  Use --force to continue.

Aborted due to warnings.

READ THIS: https://git.io/brew-troubleshooting
If reporting this issue please do so at (not Homebrew/brew):
  https://github.com/grafana/homebrew-grafana/issues

Do you guys know how we fix the issue and how I can install the grafana? Thanks in advance!