st_mtime_ns test fail on netbsd

[ThomasWaldmann]

self = <borg.testsuite.archiver.ArchiverTestCase testMethod=test_overwrite>

    def test_overwrite(self):
        self.create_regular_file('file1', size=1024 * 80)
        self.create_regular_file('dir2/file2', size=1024 * 80)
        self.cmd('init', self.repository_location)
        self.cmd('create', self.repository_location + '::test', 'input')
        # Overwriting regular files and directories should be supported
        os.mkdir('output/input')
        os.mkdir('output/input/file1')
        os.mkdir('output/input/dir2')
        with changedir('output'):
            self.cmd('extract', self.repository_location + '::test')
>       self.assert_dirs_equal('input', 'output/input')

py34/lib/python3.4/site-packages/borg/testsuite/archiver.py:405: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
py34/lib/python3.4/site-packages/borg/testsuite/__init__.py:53: in assert_dirs_equal
    self._assert_dirs_equal_cmp(diff)
py34/lib/python3.4/site-packages/borg/testsuite/__init__.py:84: in _assert_dirs_equal_cmp
    self.assert_equal(d1, d2)
E   AssertionError: Lists differ: ['dir2', 16832, 1000, 0, 1132527, 0, 2, 1442345591007673321, {}] != ['dir2', 16832, 1000, 0, 1135623, 0, 2, 1442345591007673000, {}]
E   
E   First differing element 4:
E   1132527
E   1135623
E   
E   - ['dir2', 16832, 1000, 0, 1132527, 0, 2, 1442345591007673321, {}]
E   ?                              ^^^                        ^^^
E   
E   + ['dir2', 16832, 1000, 0, 1135623, 0, 2, 1442345591007673000, {}]
E   ?                             ++ ^                        ^^^

The order of items in that list is: filename, st_mode, st_uid, st_gid, st_rdev, st_nlink, st_mtime_ns, xattr_dict.

The st_rdev difference is maybe similar cause as on openbsd, see issue #203.

So, st_mtime_ns seems to have less resolution here somehow.
This difference only happens on netbsd - not on linux, freebsd, darwin.

Reproducing:

vagrant up netbsd
vagrant ssh netbsd

Then:

cd /vagrant/borg
. borg-env/bin/activate
cd borg
tox

[ThomasWaldmann]

jborg/attic#304 somehow similar granularity / rounding issue.