minor #19310 Make the exception message more clear. (Nyholm)

This PR was submitted for the master branch but it was merged into the 2.7 branch instead (closes #19310).

Discussion
----------

Make the exception message more clear.

| Q             | A
| ------------- | ---
| Branch?       | "master"
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

A small change that makes the error message more clear. If your property is named "type", "value" or something similar it is not obvious that we refer to the property name.

See example: schmittjoh/JMSTranslationBundle#373

Commits
-------

6344ccd Make the exception message more clear.

Author: fabpot

src/Symfony/Component/Validator/Mapping/PropertyMetadata.php

@@ -39,7 +39,7 @@ class PropertyMetadata extends MemberMetadata
     public function __construct($class, $name)
     {
         if (!property_exists($class, $name)) {
-            throw new ValidatorException(sprintf('Property %s does not exist in class %s', $name, $class));
+            throw new ValidatorException(sprintf('Property "%s" does not exist in class "%s"', $name, $class));
         }
 
         parent::__construct($class, $name, $name);