Fix warning on file_get_contents

Author: alecsammon

src/JsonSchema/Uri/Retrievers/FileGetContents.php

@@ -32,8 +32,13 @@ public function retrieve($uri)
                 'method' => 'GET',
                 'header' => "Accept: " . Validator::SCHEMA_MEDIA_TYPE
             )));
-        
+
+        set_error_handler(function() use ($uri) {
+            throw new ResourceNotFoundException('JSON schema not found at ' . $uri);
+        });
         $response = file_get_contents($uri);
+        restore_error_handler();
+
         if (false === $response) {
             throw new ResourceNotFoundException('JSON schema not found at ' . $uri);
         }