Rule source on GitHub

DowngradeNonCapturingCatchesRector

Downgrade catch () without variable to one

 class SomeClass
 {
     public function run()
     {
         try {
             // code
-        } catch (\Exception) {
+        } catch (\Exception $exception) {
             // error
         }
     }
 }

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\DowngradePhp80\Rector\Catch_\DowngradeNonCapturingCatchesRector;

return RectorConfig::configure()
    ->withRules([
        DowngradeNonCapturingCatchesRector::class,
    ]);