tests: fix http-bad-server expected errors for python 3.10 (issue6643) The format of the error message changed with this version of Python. This also removes obsolete Python 3 checks.

import sys

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