MDL-68445 behat: Bump to 3.6.x

composer.lock generated with PHP 7.1, following:

https://docs.moodle.org/dev/Composer#How_to_prepare_and_submit_composer_changes

Also, ensure Symfony/Process > 4.0 compatibility
(needed for parallel runs)

composer.json

@@ -13,7 +13,7 @@
     "require-dev": {
         "phpunit/phpunit": "7.5.*",
         "phpunit/dbunit": "4.0.*",
-        "moodlehq/behat-extension": "3.38.4",
+        "moodlehq/behat-extension": "3.38.5",
         "mikey179/vfsstream": "^1.6",
         "instaclick/php-webdriver": "dev-local as 1.x-dev"
     }

lib/behat/lib.php

@@ -517,7 +517,14 @@ function cli_execute_parallel($cmds, $cwd = null, $delay = 0) {
 
     // Create child process.
     foreach ($cmds as $name => $cmd) {
-        $process = new Symfony\Component\Process\Process($cmd);
+        if (method_exists('\\Symfony\\Component\\Process\\Process', 'fromShellCommandline')) {
+            // Process 4.2 and up.
+            $process = Symfony\Component\Process\Process::fromShellCommandline($cmd);
+        } else {
+            // Process 4.1 and older.
+            $process = new Symfony\Component\Process\Process(null);
+            $process->setCommandLine($cmd);
+        }
 
         $process->setWorkingDirectory($cwd);
         $process->setTimeout(null);