skip Vulcain-based tests if the binary cannot be executed

Author: xabbuh

Tests/CurlHttpClientTest.php

@@ -169,6 +169,14 @@ private function getVulcainClient(): CurlHttpClient
         sleep('\\' === \DIRECTORY_SEPARATOR ? 10 : 1);
 
         if (!$process->isRunning()) {
+            if ('\\' !== \DIRECTORY_SEPARATOR && 127 === $process->getExitCode()) {
+                $this->markTestSkipped('vulcain binary is missing');
+            }
+
+            if ('\\' !== \DIRECTORY_SEPARATOR && 126 === $process->getExitCode()) {
+                $this->markTestSkipped('vulcain binary is not executable');
+            }
+
             throw new ProcessFailedException($process);
         }