tests/seq.py

windows: gracefully handle when the username cannot be determined

This assumes implementation details, but I don't see any other way than to check
the environment variables ourselves (which would miss out on any future
enhancements that Python may make).  This was originally reported as
https://foss.heptapod.net/mercurial/tortoisehg/thg/-/issues/5835.

#!/usr/bin/env python3
#
# A portable replacement for 'seq'
#
# Usage:
#   seq STOP              [1, STOP] stepping by 1
#   seq START STOP        [START, STOP] stepping by 1
#   seq START STEP STOP   [START, STOP] stepping by STEP

import os
import sys

try:
    import msvcrt

    msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY)
    msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
    msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY)
except ImportError:
    pass

start = 1
if len(sys.argv) > 2:
    start = int(sys.argv[1])

step = 1
if len(sys.argv) > 3:
    step = int(sys.argv[2])

stop = int(sys.argv[-1]) + 1

for i in range(start, stop, step):
    print(i)