providers/virtualbox: fix error if no snapshots

plugins/providers/virtualbox/action/snapshot_list.rb

@@ -14,6 +14,11 @@ module VagrantPlugins
             env[:machine].ui.output(snapshot, prefix: false)
           end
 
+          if snapshots.empty?
+            env[:machine].ui.output(I18n.t("vagrant.actions.vm.snapshot.list_none"))
+            env[:machine].ui.detail(I18n.t("vagrant.actions.vm.snapshot.list_none_detail"))
+          end
+
           @app.call(env)
         end
       end

plugins/providers/virtualbox/driver/base.rb

@@ -386,7 +386,8 @@ module VagrantPlugins
             if errored
               raise Vagrant::Errors::VBoxManageError,
                 command: command.inspect,
-                stderr:  r.stderr
+                stderr:  r.stderr,
+                stdout:  r.stdout
             end
           end
 

plugins/providers/virtualbox/driver/version_5_0.rb

@@ -116,10 +116,11 @@ module VagrantPlugins
         end
 
         def list_snapshots(machine_id)
-          result = []
           output = execute(
             "snapshot", machine_id, "list", "--machinereadable",
             retryable: true)
+
+          result = []
           output.split("\n").each do |line|
             if line =~ /^SnapshotName.*?="(.+?)"$/i
               result << $1.to_s
@@ -127,6 +128,9 @@ module VagrantPlugins
           end
 
           result.sort
+        rescue Vagrant::Errors::VBoxManageError => e
+          return [] if e.extra_data[:stdout].include?("does not have")
+          raise
         end
 
         def restore_snapshot(machine_id, snapshot_name)

templates/locales/en.yml

@@ -1770,6 +1770,13 @@ en:
             Deleting the snapshot '%{name}'...
           deleted: |-
             Snapshot deleted!
+          list_none: |-
+            No snapshots have been taken yet!
+          list_none_detail: |-
+            You can take a snapshot using `vagrant snapshot save`. Note that
+            not all providers support this yet. Once a snapshot is taken, you
+            can list them using this command, and use commands such as
+            `vagrant snapshot restore` to go back to a certain snapshot.
           restoring: |-
             Restoring the snapshot '%{name}'...
           saving: |-