// Mixins
// --------------------------------------------------
vendors = official

percentage($n)
  if $n == 0
    0
  else
    unit($n * 100, "%")

// Utilities

@import "mixins/hide-text"
@import "mixins/opacity"
@import "mixins/image"
@import "mixins/labels"
@import "mixins/reset-filter"
@import "mixins/resize"
@import "mixins/responsive-visibility"
@import "mixins/size"
@import "mixins/tab-focus"
@import "mixins/text-emphasis"
@import "mixins/text-overflow"
@import "mixins/vendor-prefixes"

// Components
@import "mixins/alerts"
@import "mixins/buttons"
@import "mixins/panels"
@import "mixins/pagination"
@import "mixins/list-group"
@import "mixins/nav-divider"
@import "mixins/forms"
@import "mixins/progress-bar"
@import "mixins/table-row"

// Skins
@import "mixins/background-variant"
@import "mixins/border-radius"
@import "mixins/gradients"

// Layout
@import "mixins/clearfix"
@import "mixins/center-block"
@import "mixins/nav-vertical-align"
@import "mixins/grid-framework"
@import "mixins/grid"

// Mixins
// --------------------------------------------------
vendors ?= official

percentage($n)
  if $n == 0
    0
  else
    unit($n * 100, "%")

// Utilities

@import "mixins/hide-text"
@import "mixins/opacity"
@import "mixins/image"
@import "mixins/labels"
@import "mixins/reset-filter"
@import "mixins/resize"
@import "mixins/responsive-visibility"
@import "mixins/size"
@import "mixins/tab-focus"
@import "mixins/text-emphasis"
@import "mixins/text-overflow"
@import "mixins/vendor-prefixes"

// Components
@import "mixins/alerts"
@import "mixins/buttons"
@import "mixins/panels"
@import "mixins/pagination"
@import "mixins/list-group"
@import "mixins/nav-divider"
@import "mixins/forms"
@import "mixins/progress-bar"
@import "mixins/table-row"

// Skins
@import "mixins/background-variant"
@import "mixins/border-radius"
@import "mixins/gradients"

// Layout
@import "mixins/clearfix"
@import "mixins/center-block"
@import "mixins/nav-vertical-align"
@import "mixins/grid-framework"
@import "mixins/grid"

Make the "vendors" variable overridable
Make the "vendors" variable overridable

This fix will allow developers to front-load the `vendors` variable with a different value and prevent `bootstrap-stylus` from overriding the one that was previously set.