Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

vendor/guzzlehttp/psr7/tests/InflateStreamTest.php

@@ -0,0 +1,16 @@
+<?php
+namespace GuzzleHttp\Tests\Psr7;
+
+use GuzzleHttp\Psr7;
+use GuzzleHttp\Psr7\InflateStream;
+
+class InflateStreamtest extends \PHPUnit_Framework_TestCase
+{
+    public function testInflatesStreams()
+    {
+        $content = gzencode('test');
+        $a = Psr7\stream_for($content);
+        $b = new InflateStream($a);
+        $this->assertEquals('test', (string) $b);
+    }
+}