Missing Editor Assembly for UI

[DarkRewar]

When UI module is used, this error occurs on the 0.5 version when try to build:

Library\PackageCache\com.lignus.basetool\Runtime\UI\Editor\UICustomScriptTemplates.cs(17,10): error CS0246: The type or namespace name 'MenuItemAttribute' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.lignus.basetool\Runtime\UI\Editor\UICustomScriptTemplates.cs(17,10): error CS0246: The type or namespace name 'MenuItem' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.lignus.basetool\Runtime\UI\Editor\UICustomScriptTemplates.cs(17,59): error CS0246: The type or namespace name 'priority' could not be found (are you missing a using directive or an assembly reference?)