我正在使用react、webpack bootstrap和sass来构建一个页面。在使用webpack构建包时，sass-loader在bootstrap的官方sass文件夹中包含的一个文件中的一行抛出错误。
下面是错误：The error message
我有一个styles.scss文件，它导入引导sass文件并覆盖其变量。以下是目录结构：Directory structure of the project
下面是发生错误的_maps.scss文件：

// Re-assigned maps
//
// Placed here so that others can override the default Sass maps and see automatic updates to utilities and more.

// scss-docs-start theme-colors-rgb
$theme-colors-rgb: map-loop($theme-colors, to-rgb, "$value") !default;
// scss-docs-end theme-colors-rgb

$theme-colors-text: (
  "primary": $primary-text,
  "secondary": $secondary-text,
  "success": $success-text,
  "info": $info-text,
  "warning": $warning-text,
  "danger": $danger-text,
  "light": $light-text,
  "dark": $dark-text,
) !default;

$theme-colors-bg-subtle: (
  "primary": $primary-bg-subtle,
  "secondary": $secondary-bg-subtle,
  "success": $success-bg-subtle,
  "info": $info-bg-subtle,
  "warning": $warning-bg-subtle,
  "danger": $danger-bg-subtle,
  "light": $light-bg-subtle,
  "dark": $dark-bg-subtle,
) !default;

$theme-colors-border-subtle: (
  "primary": $primary-border-subtle,
  "secondary": $secondary-border-subtle,
  "success": $success-border-subtle,
  "info": $info-border-subtle,
  "warning": $warning-border-subtle,
  "danger": $danger-border-subtle,
  "light": $light-border-subtle,
  "dark": $dark-border-subtle,
) !default;

// Utilities maps
//
// Extends the default `$theme-colors` maps to help create our utilities.

// Come v6, we'll de-dupe these variables. Until then, for backward compatibility, we keep them to reassign.
// scss-docs-start utilities-colors
$utilities-colors: $theme-colors-rgb !default;
// scss-docs-end utilities-colors

// scss-docs-start utilities-text-colors
$utilities-text: map-merge(
  $utilities-colors,
  (
    "black": to-rgb($black),
    "white": to-rgb($white),
    "body": to-rgb($body-color)
  )
) !default;
$utilities-text-colors: map-loop($utilities-text, rgba-css-var, "$key", "text") !default;

$utilities-text-emphasis-colors: (
  "primary-emphasis": var(--#{$prefix}primary-text),
  "secondary-emphasis": var(--#{$prefix}secondary-text),
  "success-emphasis": var(--#{$prefix}success-text),
  "info-emphasis": var(--#{$prefix}info-text),
  "warning-emphasis": var(--#{$prefix}warning-text),
  "danger-emphasis": var(--#{$prefix}danger-text),
  "light-emphasis": var(--#{$prefix}light-text),
  "dark-emphasis": var(--#{$prefix}dark-text)
) !default;
// scss-docs-end utilities-text-colors

// scss-docs-start utilities-bg-colors
$utilities-bg: map-merge(
  $utilities-colors,
  (
    "black": to-rgb($black),
    "white": to-rgb($white),
    "body": to-rgb($body-bg)
  )
) !default;
$utilities-bg-colors: map-loop($utilities-bg, rgba-css-var, "$key", "bg") !default;

$utilities-bg-subtle: (
  "primary-subtle": var(--#{$prefix}primary-bg-subtle),
  "secondary-subtle": var(--#{$prefix}secondary-bg-subtle),
  "success-subtle": var(--#{$prefix}success-bg-subtle),
  "info-subtle": var(--#{$prefix}info-bg-subtle),
  "warning-subtle": var(--#{$prefix}warning-bg-subtle),
  "danger-subtle": var(--#{$prefix}danger-bg-subtle),
  "light-subtle": var(--#{$prefix}light-bg-subtle),
  "dark-subtle": var(--#{$prefix}dark-bg-subtle)
) !default;
// $utilities-bg-subtle-colors: map-loop($utilities-bg-subtle, rgba-css-var, "$key", "bg") !default;
// scss-docs-end utilities-bg-colors

// scss-docs-start utilities-border-colors
$utilities-border: map-merge(
  $utilities-colors,
  (
    "white": to-rgb($white)
  )
) !default;
$utilities-border-colors: map-loop($utilities-border, rgba-css-var, "$key", "border") !default;

$utilities-border-subtle: (
  "primary-subtle": var(--#{$prefix}primary-border-subtle),
  "secondary-subtle": var(--#{$prefix}secondary-border-subtle),
  "success-subtle": var(--#{$prefix}success-border-subtle),
  "info-subtle": var(--#{$prefix}info-border-subtle),
  "warning-subtle": var(--#{$prefix}warning-border-subtle),
  "danger-subtle": var(--#{$prefix}danger-border-subtle),
  "light-subtle": var(--#{$prefix}light-border-subtle),
  "dark-subtle": var(--#{$prefix}dark-border-subtle)
) !default;
// scss-docs-end utilities-border-colors

$negative-spacers: if($enable-negative-margins, negativify-map($spacers), null) !default;

$gutters: $spacers !default;