Add $popover-border-width; refs #18150

scss/_popover.scss

@@ -12,7 +12,7 @@
   font-size: $font-size-sm;
   background-color: $popover-bg;
   background-clip: padding-box;
-  border: 1px solid $popover-border-color;
+  border: $popover-border-width solid $popover-border-color;
   @include border-radius($border-radius-lg);
   @include box-shadow(0 5px 10px rgba(0,0,0,.2));
 
@@ -107,7 +107,7 @@
   margin: 0; // reset heading margin
   font-size: $font-size-base;
   background-color: $popover-title-bg;
-  border-bottom: 1px solid darken($popover-title-bg, 5%);
+  border-bottom: $popover-border-width solid darken($popover-title-bg, 5%);
   @include border-radius(($border-radius-lg - 1) ($border-radius-lg - 1) 0 0);
 }
 

scss/_variables.scss

@@ -479,6 +479,7 @@ $tooltip-arrow-color:         $tooltip-bg !default;
 
 $popover-bg:                          #fff !default;
 $popover-max-width:                   276px !default;
+$popover-border-width:                $border-width !default;
 $popover-border-color:                rgba(0,0,0,.2) !default;
 
 $popover-title-bg:                    darken($popover-bg, 3%) !default;