test_infer_cftime_datetime_units failing on Windows

[shoyer]

I don't know why, but this test is now failing on Python 2.7 / Windows: https://ci.appveyor.com/project/shoyer/xray/builds/19850608

================================== FAILURES ===================================
______________________ test_infer_cftime_datetime_units _______________________
    @pytest.mark.skipif(not has_cftime_or_netCDF4, reason='cftime not installed')
    def test_infer_cftime_datetime_units():
        date_types = _all_cftime_date_types()
        for date_type in date_types.values():
            for dates, expected in [
                    ([date_type(1900, 1, 1),
                      date_type(1900, 1, 2)],
                     'days since 1900-01-01 00:00:00.000000'),
                    ([date_type(1900, 1, 1, 12),
                      date_type(1900, 1, 1, 13)],
                     'seconds since 1900-01-01 12:00:00.000000'),
                    ([date_type(1900, 1, 1),
                      date_type(1900, 1, 2),
                      date_type(1900, 1, 2, 0, 0, 1)],
                     'seconds since 1900-01-01 00:00:00.000000'),
                    ([date_type(1900, 1, 1),
                      date_type(1900, 1, 2, 0, 0, 0, 5)],
                     'days since 1900-01-01 00:00:00.000000'),
                    ([date_type(1900, 1, 1), date_type(1900, 1, 8),
                      date_type(1900, 1, 16)],
                     'days since 1900-01-01 00:00:00.000000')]:
>               assert expected == coding.times.infer_datetime_units(dates)
E               AssertionError: assert 'seconds sinc...:00:00.000000' == 'hours since 1...:00:00.000000'
E                 - seconds since 1900-01-01 12:00:00.000000
E                 ?  ------
E                 + hours since 1900-01-01 12:00:00.000000
E                 ? ++++

@spencerkclark please take a look (or we can xfail this if necessary)