🔨 also rewrite the stubtest stderr output

Author: jorenham

tool/stubtest.py

@@ -128,10 +128,10 @@ def main() -> int:
         capture_output=True,
         env={"FORCE_COLOR": "1"} | os.environ,
     )
-    sys.stderr.buffer.write(result.stderr)
-    output = _rewrite_mypy_output(result.stdout)
-    sys.stdout.buffer.write(output)
-    sys.stdout.buffer.flush()
+    for std in "stdout", "stderr":
+        stream = getattr(sys, std)
+        stream.buffer.write(_rewrite_mypy_output(getattr(result, std)))
+        stream.buffer.flush()
 
     return result.returncode