PriorityCallbacks: Execute callbacks before Codeception's

GitPreparer now registers a "priority" register_shutdown_function
callback in order to clean up in case of a fatal error.

lib/PriorityCallbacks.php

@@ -0,0 +1,46 @@
+<?php
+/**
+ * Execute callbacks before Codeception does
+ */
+
+class PriorityCallbacks
+{
+	/** @var array */
+	private $shutdown_functions = [];
+
+	private function __construct()
+	{
+		register_shutdown_function([$this, 'call_shutdown_functions']);
+	}
+
+	public static function instance()
+	{
+		static $instance = null;
+		if (!$instance instanceof self)
+		{
+			$instance = new static();
+		}
+		return $instance;
+	}
+
+	public function call_shutdown_functions()
+	{
+		foreach ($this->shutdown_functions as $shutdown_function)
+		{
+			call_user_func($shutdown_function);
+		}
+	}
+
+	public function register_shutdown_function($callable)
+	{
+		$this->shutdown_functions[] = $callable;
+	}
+
+	private function __clone() {}
+
+	private function __sleep() {}
+
+	private function __wakeup() {}
+}
+
+PriorityCallbacks::instance();