Tox cannot remove readonly files from tmp directory

[robgom]

When there are some read-only files left in tmp directory, they are not cleared upon next execution.

Cleaning is done in ensure_empty_dir.

Changing it to the following code fixes the problem:

import os, stat
import shutil

from tox import reporter


def ensure_empty_dir(path):
    if path.check():
        reporter.info("  removing {}".format(path))
        shutil.rmtree(str(path), onerror=remove_readonly)  # originally without onerror, just with ignore_errors
        path.ensure(dir=1)

def remove_readonly(func, path, _):
    "Clear the readonly bit and reattempt the removal"
    os.chmod(path, stat.S_IWRITE)
    func(path)

In our case those read-only files come from externally executed commands and they affect subsequent tests execution.
As a workaround we'd consider cleaning them ourselves.

Reproducible: always
Platform: win32 (Windows 10), Python 3.9
Tox version: tox==3.25.1

Please let me know if you need more information.
I can try providing self-reproducible setup, but might take a while.

[gaborbernat]

A PR adding this would we welcomed 👍

[robgom]

If you find this change ok, will try to provide an MR this week.

[robgom]

#2501
Will work further on that - wanted to share proof-of-concept.