Bottom border of 'popover-header' does not respect value specified for $popover-border-color

Created by: brneor

When customizing Bootstrap, setting a new value for $popover-border-color does not affect the value for border-bottom of elements with popover-header class.

The same does not occur when setting a new value for $card-border-color, where card-header get the correct color for border-bottom.

From _card.scss:

.card-header {
  padding: $card-cap-padding-y $card-cap-padding-x;
  margin-bottom: 0; // Removes the default margin-bottom of <hN>
  color: $card-cap-color;
  background-color: $card-cap-bg;
  border-bottom: $card-border-width solid $card-border-color;

  &:first-child {
    @include border-radius($card-inner-border-radius $card-inner-border-radius 0 0);
  }
}

From _popover.scss:

.popover-header {
  padding: $popover-header-padding-y $popover-header-padding-x;
  margin-bottom: 0; // Reset the default from Reboot
  @include font-size($font-size-base);
  color: $popover-header-color;
  background-color: $popover-header-bg;
  border-bottom: $popover-border-width solid shade-color($popover-header-bg, 10%);
  @include border-top-radius($popover-inner-border-radius);

  &:empty {
    display: none;
  }
}