I get the above error while upgrading from Magento 2.1.8 to Magento 2.2.1

> 
> 
> ```
> 2 exception(s):
> Exception #0 (ReflectionException): Class Magento\Framework\View\Layout\Reader\Visibility\Condition does not
> 
> ```
> 
> exist
> 
> 
>