error while removing tmp file on windows when downloading extends fails

[Roman Lacko]

when running on windows, and the buildout fails to download the extens, the windows error is raised ecause the tmp file is locked:

here is the code that failes, download.py, line 179 - 187:

            try:
                tmp_path, headers = urllib.urlretrieve(url, tmp_path)
                if not check_md5sum(tmp_path, md5sum):
                    raise ChecksumError(
                        'MD5 checksum mismatch downloading %r' % url)
            except IOError, e:
                os.remove(tmp_path)
                raise zc.buildout.UserError("Error downloading extends for URL"
                                            " %s: %r" % (url, e[1:3]))

the os.remove(tmp_path) raises following error on windows:
Traceback (most recent call last):
  File "C:\Buildouts\plone43wsgi\lib\site-packages\zc\buildout\buildout.py", line 1851, in main
    command)
  File "C:\Buildouts\plone43wsgi\lib\site-packages\zc\buildout\buildout.py", line 203, in __init__
    data['buildout'].copy(), override, set()))
  File "C:\Buildouts\plone43wsgi\lib\site-packages\zc\buildout\buildout.py", line 1489, in _open
    downloaded)
  File "C:\Buildouts\plone43wsgi\lib\site-packages\zc\buildout\buildout.py", line 1434, in _open
    path, is_temp = download(filename)
  File "C:\Buildouts\plone43wsgi\lib\site-packages\zc\buildout\download.py", line 99, in __call__
    local_path, is_temp = self.download(url, md5sum, path)
  File "C:\Buildouts\plone43wsgi\lib\site-packages\zc\buildout\download.py", line 185, in download
    os.remove(tmp_path)
WindowsError: [Error 32] The process cannot access the file because it is being used by another process: 'c:\\users\\rlacko~1.tem\\appdata\\local\\temp\\buildout-1qrvkz'

Regards
Roman