[Form] Added missing use statements (closes #2880)

src/Symfony/Component/Form/Extension/Core/DataTransformer/ArrayToBooleanChoicesTransformer.php

@@ -13,6 +13,7 @@ namespace Symfony\Component\Form\Extension\Core\DataTransformer;
 
 use Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceListInterface;
 use Symfony\Component\Form\DataTransformerInterface;
+use Symfony\Component\Form\Exception\TransformationFailedException;
 use Symfony\Component\Form\Exception\UnexpectedTypeException;
 
 class ArrayToBooleanChoicesTransformer implements DataTransformerInterface

src/Symfony/Component/Form/Extension/Core/DataTransformer/ScalarToBooleanChoicesTransformer.php

@@ -13,6 +13,7 @@ namespace Symfony\Component\Form\Extension\Core\DataTransformer;
 
 use Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceListInterface;
 use Symfony\Component\Form\DataTransformerInterface;
+use Symfony\Component\Form\Exception\TransformationFailedException;
 use Symfony\Component\Form\Exception\UnexpectedTypeException;
 use Symfony\Component\Form\Util\FormUtil;