Don't use is_resource() on non-streams

Author: nicolas-grekas

Terminal.php

@@ -158,8 +158,7 @@ private static function readFromProcess(string $command): ?string
 
         $cp = \function_exists('sapi_windows_cp_set') ? sapi_windows_cp_get() : 0;
 
-        $process = proc_open($command, $descriptorspec, $pipes, null, null, ['suppress_errors' => true]);
-        if (!\is_resource($process)) {
+        if (!$process = proc_open($command, $descriptorspec, $pipes, null, null, ['suppress_errors' => true])) {
             return null;
         }