Improve exception message

src/exceptions/ProcessControlExtensionNotLoadedException.php

@@ -9,8 +9,33 @@
  */
 namespace SebastianBergmann\Invoker;
 
+use function extension_loaded;
+use function function_exists;
+use function implode;
 use RuntimeException;
 
 final class ProcessControlExtensionNotLoadedException extends RuntimeException implements Exception
 {
+    public function __construct()
+    {
+        $message = [];
+
+        if (!extension_loaded('pcntl')) {
+            $message[] = 'The pcntl (process control) extension for PHP must be loaded.';
+        }
+
+        if (!function_exists('pcntl_signal')) {
+            $message[] = 'The pcntl_signal() function must not be disabled.';
+        }
+
+        if (!function_exists('pcntl_async_signals')) {
+            $message[] = 'The pcntl_async_signals() function must not be disabled.';
+        }
+
+        if (!function_exists('pcntl_alarm')) {
+            $message[] = 'The pcntl_alarm() function must not be disabled.';
+        }
+
+        parent::__construct(implode(PHP_EOL, $message));
+    }
 }