rake webpack: fixing deprecation issue

#343

Author: fiedl

Rakefile

@@ -37,30 +37,30 @@ task :webpack => 'webpack:build'
 
 namespace :webpack do
   task :build => ['build:development', 'build:production']
-  
+
   namespace :build do
     task :development => 'yarn:install' do
-      Bundler.with_clean_env do
+      Bundler.with_unbundled_env do
         sh "cd builder && bin/webpack"
       end
     end
     task :production => 'yarn:install' do
-      Bundler.with_clean_env do
+      Bundler.with_unbundled_env do
         sh "cd builder && bin/rake webpacker:compile"
       end
     end
   end
-  
+
   task :watch => 'yarn:install' do
-    Bundler.with_clean_env do
+    Bundler.with_unbundled_env do
       sh "cd builder && bin/webpack --watch"
     end
   end
-  
+
   namespace :yarn do
     task :install do
       sh "yarn install && cd builder && yarn install"
     end
   end
-end 
+end