doc/docchecker

tests: use venv on Python 3

This test was failing in some Python 3 environments because
`$PYTHON -m virtualenv` was somehow resulting in Python 2
being used. Why, I'm not sure.

Python 3 includes virtualenv in the standard library as the
`venv` module.

This commit changes test-install.t to use `$PYTHON -m venv` on
Python 3 and `$PYTHON -m virtualenv` on Python 2 (if available).

I chose to make some test output duplicated because we can't
have nested conditionals and there is no easy way to express
ORing of hghave checks.

Differential Revision: https://phab.mercurial-scm.org/D7224

#!/usr/bin/env python
#
# docchecker - look for problematic markup
#
# Copyright 2016 timeless <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import, print_function

import os
import re
import sys

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

stdout = getattr(sys.stdout, 'buffer', sys.stdout)

leadingline = re.compile(br'(^\s*)(\S.*)$')

checks = [
  (br""":hg:`[^`]*'[^`]*`""",
   b"""warning: please avoid nesting ' in :hg:`...`"""),
  (br'\w:hg:`',
   b'warning: please have a space before :hg:'),
  (br"""(?:[^a-z][^'.])hg ([^,;"`]*'(?!hg)){2}""",
   b'''warning: please use " instead of ' for hg ... "..."'''),
]

def check(line):
    messages = []
    for match, msg in checks:
        if re.search(match, line):
            messages.append(msg)
    if messages:
        stdout.write(b'%s\n' % line)
        for msg in messages:
            stdout.write(b'%s\n' % msg)

def work(file):
    (llead, lline) = (b'', b'')

    for line in file:
        # this section unwraps lines
        match = leadingline.match(line)
        if not match:
            check(lline)
            (llead, lline) = (b'', b'')
            continue

        lead, line = match.group(1), match.group(2)
        if (lead == llead):
            if (lline != b''):
                lline += b' ' + line
            else:
                lline = line
        else:
            check(lline)
            (llead, lline) = (lead, line)
    check(lline)

def main():
    for f in sys.argv[1:]:
        try:
            with open(f, 'rb') as file:
                work(file)
        except BaseException as e:
            sys.stdout.write(r"failed to process %s: %s\n" % (f, e))

main()