Index: frontend/node_modules/postcss-js/async.js
===================================================================
--- frontend/node_modules/postcss-js/async.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/postcss-js/async.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,15 @@
+let postcss = require('postcss')
+
+let parse = require('./parser')
+let processResult = require('./process-result')
+
+module.exports = function async(plugins) {
+  let processor = postcss(plugins)
+  return async input => {
+    let result = await processor.process(input, {
+      parser: parse,
+      from: undefined
+    })
+    return processResult(result)
+  }
+}