title: How to change the default message in Respect Validation?
body: <p>I use Respect Validation for password matches on a Slim app:</p>
  
  <pre><code>class PasswordController extends Controller
  {
      ;
      ;
      public function postChangePassword($request, $response) { 
          $validation = $this-&gt;validator-&gt;validate($request, [
              'password_old' =&gt; v::noWhitespace()-&gt;notEmpty()-&gt;matchesPassword($this-&gt;auth-&gt;user()-&gt;password),
              'password' =&gt; v::noWhitespace()-&gt;notEmpty()
          ]);
  
          if($validation-&gt;failed()) { 
              // stay on the same page
          }
  
          die('update password');
      }
  }
  </code></pre>
  
  <p>I can authenticate the password:</p>
  
  <pre><code>class MatchesPassword extends AbstractRule 
  {
      protected $password;
  
      public function __construct($password) { 
          $this-&gt;password = $password;
      }
  
      public function validate($input) { 
          // compare the non-hashed input with the already hashed password
      }
  }
  </code></pre>
  
  <p>...and I created my own custom string for the 3rd rule ('password_old'):</p>
  
  <pre><code>class MatchesPasswordException extends ValidationException 
  {
      public static $defaultTemplates = [
          self::MODE_DEFAULT =&gt; [
              self::STANDARD =&gt; 'Password does not match.',
          ],
      ];
  }
  </code></pre>
  
  <p>The script works fine, I get the following message when I submit with   <strong><em>'password_old'</em></strong> field empty:<br>
  "<strong>Password_old must not be empty</strong>"</p>
  
  <p>I would like to change the above default message to a custom string, e.g.:<br>
  "<strong>The value must not be empty</strong>"</p>