Add test for --configuration CLI option being used with path to configuration file that does not exist

Author: sebastianbergmann

tests/end-to-end/generic/configuration-does-not-exist.phpt

@@ -0,0 +1,15 @@
+--TEST--
+phpunit --configuration does-not-exist.xml
+--FILE--
+<?php declare(strict_types=1);
+$_SERVER['argv'][] = '--do-not-cache-result';
+$_SERVER['argv'][] = '--configuration';
+$_SERVER['argv'][] = 'does-not-exist.xml';
+
+require_once __DIR__ . '/../../bootstrap.php';
+
+(new PHPUnit\TextUI\Application)->run($_SERVER['argv']);
+--EXPECTF--
+PHPUnit %s by Sebastian Bergmann and contributors.
+
+Could not read XML from file "does-not-exist.xml"