tests: use `test -f` instead of `ls` to see if a file is present (issue6662) ls's exit code when file doesn't exist is 2 on Linux and 1 on NetBSD, so let's use something that's supposedly more portable, since we only care whether the file is there or not.

import sys

for line in sys.stdin:
    if line.lower() in ("message-id: \n", "in-reply-to: \n"):
        line = line[:-2]
    print(line, end="")