Child UIs successfully set environment to themselves

lib/vagrant/environment.rb

@@ -138,8 +138,13 @@ module Vagrant
     # Returns the {UI} for the environment, which is responsible
     # for talking with the outside world.
     def ui
-      return parent.ui if parent
-      @ui ||= UI.new(self)
+      @ui ||= if parent
+        result = parent.ui.clone
+        result.env = self
+        result
+      else
+        UI.new(self)
+      end
     end
 
     #---------------------------------------------------------------

lib/vagrant/ui.rb

@@ -5,7 +5,7 @@ module Vagrant
   # through a shell). They must respond to the typically logger methods
   # of `warn`, `error`, `info`, and `confirm`.
   class UI
-    attr_reader :env
+    attr_accessor :env
 
     def initialize(env)
       @env = env