Merge branch '4.2'

* 4.2:
  [HttpFoundation] Check file exists before unlink
  [Console] Fixed #29835: ConfirmationQuestion with default true for answer '0'
  [Cache] PDO-based cache pool table autocreation does not work
  [Translation] Concatenated translation messages
  [Form] ensure compatibility with older PHPUnit mocks
  [Serializer] Docblock about throwing exceptions on serializer
  [Cache] fix used variable name
  [Debug][ErrorHandler] Preserve our error handler when a logger set another one
  [Form] Changed UrlType input type to text when default_protocol is not null
  [Bugfix] MemcachedSessionHandler::close() must close connection
  Always pass $key to NullAdapter->createCacheItem

Author: nicolas-grekas

Tests/Validator/TraceableValidatorTest.php

@@ -15,7 +15,6 @@
 use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\ConstraintViolation;
 use Symfony\Component\Validator\ConstraintViolationList;
-use Symfony\Component\Validator\ConstraintViolationListInterface;
 use Symfony\Component\Validator\Context\ExecutionContextInterface;
 use Symfony\Component\Validator\Mapping\MetadataInterface;
 use Symfony\Component\Validator\Validator\ContextualValidatorInterface;
@@ -87,13 +86,13 @@ public function testForwardsToOriginalValidator()
         $expects('startContext')->willReturn($expected = $this->createMock(ContextualValidatorInterface::class));
         $this->assertSame($expected, $validator->startContext(), 'returns original validator startContext() result');
 
-        $expects('validate')->willReturn($expected = $this->createMock(ConstraintViolationListInterface::class));
+        $expects('validate')->willReturn($expected = new ConstraintViolationList());
         $this->assertSame($expected, $validator->validate('value'), 'returns original validator validate() result');
 
-        $expects('validateProperty')->willReturn($expected = $this->createMock(ConstraintViolationListInterface::class));
+        $expects('validateProperty')->willReturn($expected = new ConstraintViolationList());
         $this->assertSame($expected, $validator->validateProperty(new \stdClass(), 'property'), 'returns original validator validateProperty() result');
 
-        $expects('validatePropertyValue')->willReturn($expected = $this->createMock(ConstraintViolationListInterface::class));
+        $expects('validatePropertyValue')->willReturn($expected = new ConstraintViolationList());
         $this->assertSame($expected, $validator->validatePropertyValue(new \stdClass(), 'property', 'value'), 'returns original validator validatePropertyValue() result');
     }