VBoxManage errors show stderr

CHANGELOG.md

@@ -9,6 +9,8 @@ IMPROVEMENTS:
   - Vagrant will detect Bundler environments, make assumptions that you're
     developing plugins, and will quiet its error output a bit.
   - More comprehensive synced folder configuration validation.
+  - VBoxManage errors now show the output from the command so that
+    users can potentially know what is wrong.
 
 BUG FIXES:
 

plugins/providers/virtualbox/driver/base.rb

@@ -279,6 +279,9 @@ module VagrantPlugins
           # Variable to store our execution result
           r = nil
 
+          # If there is an error with VBoxManage, this gets set to true
+          errored = false
+
           retryable(:on => Vagrant::Errors::VBoxManageError, :tries => tries, :sleep => 1) do
             # Execute the command
             r = raw(*command, &block)
@@ -294,7 +297,7 @@ module VagrantPlugins
                 # This is usually indicative of a corrupted VirtualBox install.
                 raise Vagrant::Errors::VBoxManageNotFoundError
               else
-                raise Vagrant::Errors::VBoxManageError, :command => command.inspect
+                errored = true
               end
             else
               # Sometimes, VBoxManage fails but doesn't actual return a non-zero
@@ -302,11 +305,19 @@ module VagrantPlugins
               # occurred.
               if r.stderr =~ /VBoxManage: error:/
                 @logger.info("VBoxManage error text found, assuming error.")
-                raise Vagrant::Errors::VBoxManageError, :command => command.inspect
+                errored = true
               end
             end
           end
 
+          # If there was an error running VBoxManage, show the error and the
+          # output.
+          if errored
+            raise Vagrant::Errors::VBoxManageError,
+              :command => command.inspect,
+              :stderr  => r.stderr
+          end
+
           # Return the output, making sure to replace any Windows-style
           # newlines with Unix-style.
           r.stdout.gsub("\r\n", "\n")

templates/locales/en.yml

@@ -386,12 +386,12 @@ en:
 
         %{file}
       vboxmanage_error: |-
-        There was an error executing the following command with VBoxManage:
+        There was an error while executing `VBoxManage`, a CLI used by Vagrant
+        for controlling VirtualBox. The command and stderr is shown below.
 
-        %{command}
+        Command: %{command}
 
-        For more information on the failure, enable detailed logging by setting
-        the environment variable VAGRANT_LOG to DEBUG.
+        Stderr: %{stderr}
       vboxmanage_not_found_error: |-
         The "VBoxManage" command or one of its dependencies could not
         be found. Please verify VirtualBox is properly installed. You can verify