npm and error messages

node_modules/clean-css/lib/reader/rebase-local-map.js

@@ -0,0 +1,15 @@
+var path = require('path');
+
+function rebaseLocalMap(sourceMap, sourceUri, rebaseTo) {
+  var currentPath = path.resolve('');
+  var absoluteUri = path.resolve(currentPath, sourceUri);
+  var absoluteUriDirectory = path.dirname(absoluteUri);
+
+  sourceMap.sources = sourceMap.sources.map(function(source) {
+    return path.relative(rebaseTo, path.resolve(absoluteUriDirectory, source));
+  });
+
+  return sourceMap;
+}
+
+module.exports = rebaseLocalMap;