diff -r d5fc1b59a2df -r 27ff81547d35 tests/testlib/sigpipe-worker.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/testlib/sigpipe-worker.py	Mon Jul 12 03:30:04 2021 +0200
@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+#
+# This is literally `cat` but in python, one char at a time.
+#
+# see sigpipe-remote.py for details.
+from __future__ import print_function
+
+import io
+import os
+import sys
+
+
+if isinstance(sys.stdout.buffer, io.BufferedWriter):
+    print('SIGPIPE-WORKER: script need unbuffered output', file=sys.stderr)
+    sys.exit(255)
+
+while True:
+    c = os.read(sys.stdin.fileno(), 1)
+    os.write(sys.stdout.fileno(), c)