tests: add tests for when stdout or stderr is connected to `os.devnull`
The original motivation was that creating PTYs on Windows is not possible, but
`NUL` is recognized as a TTY, so we can have at least some test coverage for
the TTY case. I think it doesn’t hurt to run the test cases on all systems.
#!/bin/sh
HGENCODING=UTF-8
export HGENCODING
echo ".. -*- coding: utf-8 -*-" > gendoc.txt
echo "" >> gendoc.txt
LANGUAGE=$1 "$PYTHON" "$TESTDIR/../doc/gendoc.py" >> gendoc.txt 2> /dev/null || exit
echo "checking for parse errors"
"$PYTHON" "$TESTDIR/../doc/docchecker" gendoc.txt
"$PYTHON" "$TESTDIR/../doc/runrst" html gendoc.txt /dev/null