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

vendor/phpunit/php-code-coverage/src/CodeCoverage/Exception/UnintentionallyCoveredCode.php

@@ -0,0 +1,18 @@
+<?php
+/*
+ * This file is part of the PHP_CodeCoverage package.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * Exception that is raised when code is unintentionally covered.
+ *
+ * @since Class available since Release 2.0.0
+ */
+class PHP_CodeCoverage_Exception_UnintentionallyCoveredCode extends PHP_CodeCoverage_Exception
+{
+}