When migrating Landing Pages using php bin/console ezplatform:page:migrate omitting one of the zones in the layout definition will result in the exception:

In PageFactory.php line 80:
Attempted to load class "ZoneNotFoundException" from namespace "EzSystems\EzPlatformPageFieldType\Exception". Did you forget a "use" statement for another namespace?

This happens because ZoneNotFoundException was removed in version 1.1.0 of ezsystems/ezplatform-page-fieldtype, but ezsystems/ezplatform-page-migration still uses it.