[HttpFoundation] tweaked HeaderBag::__toString() to ease debugging

src/Symfony/Component/HttpFoundation/HeaderBag.php

@@ -48,10 +48,11 @@ class HeaderBag
             return preg_replace('/\-(.)/e', "'-'.strtoupper('\\1')", ucfirst($name));
         };
 
+        $max = max(array_map('strlen', array_keys($this->headers))) + 1;
         $content = '';
         foreach ($this->headers as $name => $values) {
             foreach ($values as $value) {
-                $content .= sprintf("%s: %s\r\n", $beautifier($name), $value);
+                $content .= sprintf("%-{$max}s %s\r\n", $beautifier($name).':', $value);
             }
         }