Fail as early and noisily as possible

Today, I tried using SYMFONY_PHPUNIT_VERSION=6 because I don't really
care about the minor version. I got lots of warnings, followed by
hard-to-understand error messages. This will silence the first warning
and will throw an exception instead.

Author: greg0ire

src/Symfony/Bridge/PhpUnit/bin/simple-phpunit

@@ -51,7 +51,12 @@ if (!file_exists("$PHPUNIT_DIR/phpunit-$PHPUNIT_VERSION/phpunit") || md5_file(__
         passthru(sprintf('\\' === DIRECTORY_SEPARATOR ? '(del /S /F /Q %s & rmdir %1$s) >nul': 'rm -rf %s', "phpunit-$PHPUNIT_VERSION"));
     }
     if (extension_loaded('openssl') && ini_get('allow_url_fopen') && !isset($_SERVER['http_proxy']) && !isset($_SERVER['https_proxy'])) {
-        stream_copy_to_stream(fopen("https://github.com/sebastianbergmann/phpunit/archive/$PHPUNIT_VERSION.zip", 'rb'), fopen("$PHPUNIT_VERSION.zip", 'wb'));
+        $remoteZip = "https://github.com/sebastianbergmann/phpunit/archive/$PHPUNIT_VERSION.zip";
+        $remoteZipStream = @fopen($remoteZip, 'rb');
+        if (!$remoteZipStream) {
+            throw new \RuntimeException("Could not find $remoteZip");
+        }
+        stream_copy_to_stream($remoteZipStream, fopen("$PHPUNIT_VERSION.zip", 'wb'));
     } else {
         @unlink("$PHPUNIT_VERSION.zip");
         passthru("wget https://github.com/sebastianbergmann/phpunit/archive/$PHPUNIT_VERSION.zip");