Fix lax validation of packages when loading them, fixes #3606, fixes #3605

src/Composer/Json/JsonFile.php

@@ -154,8 +154,7 @@ class JsonFile
 
         if ($schema === self::LAX_SCHEMA) {
             $schemaData->additionalProperties = true;
-            $schemaData->properties->name->required = false;
-            $schemaData->properties->description->required = false;
+            $schemaData->required = array();
         }
 
         $validator = new Validator();

src/Composer/Json/JsonValidationException.php

@@ -21,10 +21,10 @@ class JsonValidationException extends Exception
 {
     protected $errors;
 
-    public function __construct($message, $errors = array())
+    public function __construct($message, $errors = array(), \Exception $previous = null)
     {
         $this->errors = $errors;
-        parent::__construct($message);
+        parent::__construct($message, 0, $previous);
     }
 
     public function getErrors()