test: use PYTHON executable from env in assertSnapshot

PR-URL: #53938
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

test/common/assertSnapshot.js

@@ -78,8 +78,11 @@ async function spawnAndAssert(filename, transform = (x) => x, { tty = false, ...
     return;
   }
   const flags = common.parseTestFlags(filename);
-  const executable = tty ? path.join(__dirname, '../..', 'tools/pseudo-tty.py') : process.execPath;
-  const args = tty ? [process.execPath, ...flags, filename] : [...flags, filename];
+  const executable = tty ? (process.env.PYTHON || 'python3') : process.execPath;
+  const args =
+    tty ?
+      [path.join(__dirname, '../..', 'tools/pseudo-tty.py'), process.execPath, ...flags, filename] :
+      [...flags, filename];
   const { stdout, stderr } = await common.spawnPromisified(executable, args, options);
   await assertSnapshot(transform(`${stdout}${stderr}`), filename);
 }