provisioners/chef: use Subprocess to execute knife

plugins/provisioners/chef/provisioner/chef_client.rb

@@ -1,4 +1,5 @@
 require 'pathname'
+require 'vagrant/util/subprocess'
 
 require File.expand_path("../base", __FILE__)
 
@@ -108,7 +109,16 @@ module VagrantPlugins
           env[:ui].info(I18n.t(
             "vagrant.provisioners.chef.deleting_from_server",
             deletable: deletable, name: node_name))
-          Kernel.system("knife #{deletable} delete --yes #{node_name} > /dev/null 2>&1")
+
+          command = ["knife", deletable, "delete", "--yes", node_name]
+          r = Vagrant::Util::Subprocess.execute(*command)
+          if r.exit_code != 0
+            env[:ui].error(I18n.t(
+              "vagrant.chef_client_cleanup_failed",
+              deletable: deletable,
+              stdout: r.stdout,
+              stderr: r.stderr))
+          end
         end
       end
     end

templates/locales/en.yml

@@ -25,6 +25,14 @@ en:
       CFEngine running in "single run" mode. Will execute one file.
     cfengine_single_run_execute: |-
       Executing run file for CFEngine...
+    chef_client_cleanup_failed: |-
+      Cleaning up the '%{deletable}' for Chef failed. The stdout and
+      stderr are shown below. Vagrant will continue destroying the machine,
+      so please clean up these resources manually.
+
+      stdout: %{stdout}
+
+      stderr: %{stderr}
     chef_run_list_empty: |-
       Warning: Chef solo run list is empty. This may not be what you want.
     provisioner_cleanup: |-