This is a Bower package font-source-sans-pro with Source Sans Pro, open-source font face from Adobe. You can preview the font on Typecast.

This package is based on Paul D. Hunt work. Compiled web fonts are sourced from adobe-fonts/source-sans-pro, release 2.010R-ro/1.065R-it (8 Jul 2014).

Search Bower.io for font-source-sans-pro.
Simply add to your bower.json line:

   "font-source-sans-pro": "<version>",

Override $SourceSansProPath variable in your .sass files:

$SourceSansProPath: '/path/to/directory/with/font/files';

Then simply import the file:

@import 'font-source-sans-pro/source-sans-pro';

See adobe-fonts/source-sans-pro repository.