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

vendor/guzzlehttp/psr7/tests/NoSeekStreamTest.php

@@ -0,0 +1,40 @@
+<?php
+namespace GuzzleHttp\Tests\Psr7;
+
+use GuzzleHttp\Psr7;
+use GuzzleHttp\Psr7\NoSeekStream;
+
+/**
+ * @covers GuzzleHttp\Psr7\NoSeekStream
+ * @covers GuzzleHttp\Psr7\StreamDecoratorTrait
+ */
+class NoSeekStreamTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @expectedException \RuntimeException
+     * @expectedExceptionMessage Cannot seek a NoSeekStream
+     */
+    public function testCannotSeek()
+    {
+        $s = $this->getMockBuilder('Psr\Http\Message\StreamInterface')
+            ->setMethods(['isSeekable', 'seek'])
+            ->getMockForAbstractClass();
+        $s->expects($this->never())->method('seek');
+        $s->expects($this->never())->method('isSeekable');
+        $wrapped = new NoSeekStream($s);
+        $this->assertFalse($wrapped->isSeekable());
+        $wrapped->seek(2);
+    }
+
+    /**
+     * @expectedException \RuntimeException
+     * @expectedExceptionMessage Cannot write to a non-writable stream
+     */
+    public function testHandlesClose()
+    {
+        $s = Psr7\stream_for('foo');
+        $wrapped = new NoSeekStream($s);
+        $wrapped->close();
+        $wrapped->write('foo');
+    }
+}