compat: don't rely on cpython-specific builtins manipulation
Pierre Augier signaled on the mailing list that this fails on Pypy and pointed
out the correct solution.
Differential Revision: https://phab.mercurial-scm.org/D11732
from __future__ import absolute_import, print_function
import sys
for line in sys.stdin:
if line.lower() in ("message-id: \n", "in-reply-to: \n"):
line = line[:-2]
print(line, end="")