title: Bitters error ("Undefined variable: $font-stack-system")
body: <p>My folder structure:</p>
  
  <pre><code>- app
  -- sass
  --- style.scss
  --- base
  --- bourbon
  </code></pre>
  
  <p>In my style.scss I import bourbon and base (and neat):</p>
  
  <pre><code>@import "bourbon/bourbon";
  @import "base/base"; // bitters
  @import "neat/neat"; // bourbon grid
  </code></pre>
  
  <p>When I run "$gulp" (gulp is installed globally) I get the error:</p>
  
  <pre><code>[Error: app\sass\base\_variables.scss
  Error: Undefined variable: "$font-stack-system".
      on line 6 of app/sass/base/_variables.scss
  &gt;&gt; $base-font-family: $font-stack-system;
     -------------------^
  ]
    formatted: 'Error: Undefined variable: "$font-stack-system".\n        on line 6 of app/sass/base/_variables.scss\n&gt;&gt; $base-font-family: $font-stack-system;\n   -------------------^\n',
  </code></pre>
  
  <p>(+ some more "Undefined variable" errors from "base" (bitters)) When I delete the line:</p>
  
  <pre><code>@import "base/base"; // bitters
  </code></pre>
  
  <p>It works. So I think there is a file missing but I don't know which.</p>
  
  <p>EDIT: <strong>I found the error</strong> - the console always installs an old bourbon install (v. 4.x) and i need v. 5.x.</p>