title: Bootstrap 4.1.3 $font-family-base is ignored
body: <p>I'm trying to change the default font-family in Bootstrap but my changes are ignored.</p>
  
  <p>This issue is closed on the repo (<a href="https://github.com/twbs/bootstrap/issues/21595" rel="nofollow noreferrer">https://github.com/twbs/bootstrap/issues/21595</a>) but I still have the problem.</p>
  
  <pre><code>&gt; bundle info bootstrap
  =&gt; bootstrap (4.1.3)
  </code></pre>
  
  <p>I have <code>bootstrap-custom.scss</code>:</p>
  
  <pre><code>/*!
   * Bootstrap v4.1.3 (https://getbootstrap.com/)
   * Copyright 2011-2018 The Bootstrap Authors
   * Copyright 2011-2018 Twitter, Inc.
   * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
   */
  
   ...
   @import "bootstrap/variables";
   ...
  </code></pre>
  
  <p><code>_variables.scss</code>:</p>
  
  <pre><code>...
  //== Typography
  //
  //## Font, line-height, and color for body text, headings, and more.
  
  $font-family-sans-serif:  "Roboto", "Helvetica Neue", Helvetica, Arial, sans-serif !default;
  $font-family-serif:       Georgia, "Times New Roman", Times, serif !default;
  //** Default monospace fonts for `&lt;code&gt;`, `&lt;kbd&gt;`, and `&lt;pre&gt;`.
  $font-family-monospace:   Menlo, Monaco, Consolas, "Courier New", monospace !default;
  $font-family-base:        $font-family-sans-serif !default;
  ...
  </code></pre>
  
  <p>And I import it in <code>application.scss</code> at the top of my file:</p>
  
  <pre><code>@import "bootstrap-custom";
  @import "variables";
  </code></pre>
  
  <p>If I try this css, that doesn't work:</p>
  
  <pre><code>body {
    font-family: $font-family-base;
  }
  </code></pre>
  
  <p>But if I change the name of <code>$font-family-base</code> in the <code>_variables.scss</code> and use the new variable in body, it works.</p>
  
  <p>Do I something wrong?</p>