tracopt.versioncontrol.git.tests.git_fs.GitCachedRepositoryTestCase failure on Windows

[Christian Boos]

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ERROR: test_sync_too_many_merges (tracopt.versioncontrol.git.tests.git_fs.GitCachedRepositoryTestCase)
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Traceback (most recent call last):
  File "C:\projects\trac\tracopt\versioncontrol\git\tests\git_fs.py", line 112, in tearDown
    rmtree(self.repos_path)
  File "C:\projects\trac\trac\tests\compat.py", line 101, in rmtree
    shutil.rmtree(path, onerror=onerror)
  File "C:\Python27\lib\shutil.py", line 247, in rmtree
    rmtree(fullname, ignore_errors, onerror)
  File "C:\Python27\lib\shutil.py", line 247, in rmtree
    rmtree(fullname, ignore_errors, onerror)
  File "C:\Python27\lib\shutil.py", line 252, in rmtree
    onerror(os.remove, fullname, sys.exc_info())
  File "C:\projects\trac\trac\tests\compat.py", line 94, in onerror
    function(path)
WindowsError: [Error 5] Access is denied: u'c:\\users\\appveyor\\appdata\\local\\temp\\1\\trac-gitrepos-zkbb4q\\objects\\pack\\pack-a7f586d90bd005eeaba49e459c29777f62fcf408.idx'

The problem happens only on 1.0-stable, not on trunk (e.g. ​1.0-stable.45).

Also, only the stock Python 2.7.11 builds (both x86 and x64) show the issue. Of note, the Conda builds (also 2.7.11) don't have it.

I couldn't reproduce locally, but then I have a much older version of git (1.9.4.msysgit.1 vs. 2.6.3.windows.1 on AppVeyor).