UPGRADE FROM 5.2 to 5.3

Form

Changed $forms parameter type of the DataMapperInterface::mapDataToForms() method from iterable to \Traversable.
Changed $forms parameter type of the DataMapperInterface::mapFormsToData() method from iterable to \Traversable.
Deprecated passing an array as the second argument of the DataMapper::mapDataToForms() method, pass \Traversable instead.
Deprecated passing an array as the first argument of the DataMapper::mapFormsToData() method, pass \Traversable instead.
Deprecated passing an array as the second argument of the CheckboxListMapper::mapDataToForms() method, pass \Traversable instead.
Deprecated passing an array as the first argument of the CheckboxListMapper::mapFormsToData() method, pass \Traversable instead.
Deprecated passing an array as the second argument of the RadioListMapper::mapDataToForms() method, pass \Traversable instead.
Deprecated passing an array as the first argument of the RadioListMapper::mapFormsToData() method, pass \Traversable instead.

Marked the class Symfony\Component\HttpKernel\EventListener\DebugHandlersListener as internal

Deprecated voters that do not return a valid decision when calling the vote method.