Proper error handling if the shared folder cannot be created [GH-604]

lib/vagrant/action/vm/share_folders.rb

@@ -46,7 +46,12 @@ module Vagrant
             if !hostpath.directory? && options[:create]
               # Host path doesn't exist, so let's create it.
               @logger.debug("Host path doesn't exist, creating: #{hostpath}")
-              hostpath.mkpath
+
+              begin
+                hostpath.mkpath
+              rescue Errno::EACCES
+                raise Errors::SharedFolderCreateFailed, :path => hostpath.to_s
+              end
             end
           end
         end

lib/vagrant/errors.rb

@@ -268,6 +268,11 @@ module Vagrant
       error_key(:scp_unavailable)
     end
 
+    class SharedFolderCreateFailed < VagrantError
+      status_code(66)
+      error_key(:shared_folder_create_failed)
+    end
+
     class SSHAuthenticationFailed < VagrantError
       status_code(11)
       error_key(:ssh_authentication_failed)

templates/locales/en.yml

@@ -80,6 +80,14 @@ en:
       scp_unavailable: |-
         SSH server on the guest doesn't support SCP. Please install the necessary
         software to enable SCP on your guest operating system.
+      shared_folder_create_failed: |-
+        Failed to create the following shared folder on the host system. This is
+        usually because Vagrant does not have sufficient permissions to create
+        the folder.
+
+        %{path}
+
+        Please create the folder manually or specify another path to share.
       ssh_authentication_failed: |-
         SSH authentication failed! This is typically caused by the public/private
         keypair for the SSH user not being properly set on the guest VM. Please