Changed ChartIsAMethodException message

Author: szymach

src/Exception/ChartIsAMethodException.php

@@ -9,19 +9,18 @@
  */
 class ChartIsAMethodException extends FactoryException
 {
-    protected $message = 'The requested chart is not a seperate class, to draw'
-        . ' it you need to call the "%s" method on the Image object'
-        . ' after populating it with data!'
-        . ' Check the documentation on library\'s website for details.'
-    ;
-
     /**
      * @param string $method - the method which is supposed to be used
      * @param int $code
      * @param Exception $previous
      */
     public function __construct($method, $code = null, Exception $previous = null)
     {
-        parent::__construct(sprintf($this->message, $method), $code, $previous);
+        $message = 'The requested chart is not a seperate class, to draw'
+            . ' it you need to call the "%s" method on the Image object'
+            . ' after populating it with data!'
+            . ' Check the documentation on library\'s website for details.'
+        ;
+        parent::__construct(sprintf($message, $method), $code, $previous);
     }
 }