commands/plugin: error if windows with space in dir [GH-4351]

lib/vagrant/errors.rb

@@ -528,6 +528,10 @@ module Vagrant
       error_key(:plugin_install_license_not_found)
     end
 
+    class PluginInstallSpace < VagrantError
+      error_key(:plugin_install_space)
+    end
+
     class PluginInstallVersionConflict < VagrantError
       error_key(:plugin_install_version_conflict)
     end

plugins/commands/plugin/action/install_gem.rb

@@ -1,5 +1,6 @@
 require "log4r"
 require "vagrant/plugin/manager"
+require "vagrant/util/platform"
 
 module VagrantPlugins
   module CommandPlugin
@@ -18,6 +19,14 @@ module VagrantPlugins
           sources     = env[:plugin_sources]
           version     = env[:plugin_version]
 
+          # If we're on Windows and the user data path has a space in it,
+          # then things won't work because of a Ruby bug.
+          if Vagrant::Util::Platform.windows?
+            if Vagrant.user_data_path.to_s.include?(" ")
+              raise Vagrant::Errors::PluginInstallSpace
+            end
+          end
+
           # Install the gem
           plugin_name_label = plugin_name
           plugin_name_label += " --version '#{version}'" if version

templates/locales/en.yml

@@ -867,6 +867,11 @@ en:
         The license file to install could not be found. Please verify
         the path you gave is correct. The path to the license file given
         was: '%{path}'
+      plugin_install_space: |-
+        The directory where plugins are installed (the Vagrant home directory)
+        has a space in it. On Windows, there is a bug in Ruby when compiling
+        plugins into directories with spaces. Please move your Vagrant home
+        directory to a path without spaces and try again.
       plugin_install_version_conflict: |-
         The plugin(s) can't be installed due to the version conflicts below.
         This means that the plugins depend on a library version that conflicts