diff -r d4ec02c51c91 -r af15590802a4 assets/stylesheets/bootstrap/mixins/_background-variant.scss
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/assets/stylesheets/bootstrap/mixins/_background-variant.scss	Thu Jun 15 12:17:09 2017 +0200
@@ -0,0 +1,12 @@
+// Contextual backgrounds
+
+// [converter] $parent hack
+@mixin bg-variant($parent, $color) {
+  #{$parent} {
+    background-color: $color;
+  }
+  a#{$parent}:hover,
+  a#{$parent}:focus {
+    background-color: darken($color, 10%);
+  }
+}