Error trying to build using Bower & Grunt

Created by: cvrebert

$ bower install bootstrap
bower bootstrap#*               cached git://github.com/twbs/bootstrap.git#3.1.1
bower bootstrap#*             validate 3.1.1 against git://github.com/twbs/bootstrap.git#*
bower bootstrap#*                  new version for git://github.com/twbs/bootstrap.git#*
bower bootstrap#*              resolve git://github.com/twbs/bootstrap.git#*
bower bootstrap#*             download https://github.com/twbs/bootstrap/archive/v3.2.0.tar.gz
bower bootstrap#*              extract archive.tar.gz
bower bootstrap#*             resolved git://github.com/twbs/bootstrap.git#3.2.0
bower jquery#>= 1.9.0           cached git://github.com/jquery/jquery.git#2.1.0
bower jquery#>= 1.9.0         validate 2.1.0 against git://github.com/jquery/jquery.git#>= 1.9.0
bower jquery#>= 1.9.0              new version for git://github.com/jquery/jquery.git#>= 1.9.0
bower jquery#>= 1.9.0          resolve git://github.com/jquery/jquery.git#>= 1.9.0
bower jquery#>= 1.9.0         download https://github.com/jquery/jquery/archive/2.1.1.tar.gz
bower jquery#>= 1.9.0          extract archive.tar.gz
bower jquery#>= 1.9.0         resolved git://github.com/jquery/jquery.git#2.1.1
bower bootstrap#~3.2.0         install bootstrap#3.2.0
bower jquery#>= 1.9.0          install jquery#2.1.1

bootstrap#3.2.0 bower_components/bootstrap
└── jquery#2.1.1

jquery#2.1.1 bower_components/jquery
$ cd bower_components/bootstrap
$ npm install
<snipped>
$ grunt dist
Running "clean:dist" (clean) task
Cleaning dist...OK

Running "less:compileCore" (less) task
File dist/css/bootstrap.css.map created.
File dist/css/bootstrap.css created: 131.45 kB → 131.5 kB

Running "less:compileTheme" (less) task
File dist/css/bootstrap-theme.css.map created.
File dist/css/bootstrap-theme.css created: 17.85 kB → 17.89 kB

Running "autoprefixer:core" (autoprefixer) task
File dist/css/bootstrap.css created.
File dist/css/bootstrap.css.map created (source map).

Running "autoprefixer:theme" (autoprefixer) task
File dist/css/bootstrap-theme.css created.
File dist/css/bootstrap-theme.css.map created (source map).

Running "autoprefixer:docs" (autoprefixer) task
Warning: No source files were found. Use --force to continue.

Aborted due to warnings.

<snipped>