def clean_semver(cls, version_spec):
        return re.sub(r"([<>=~])\s+?v?", "\\1", version_spec, re.IGNORECASE)
def test_bad_isointervals():
    bad_intervals = [
        '2013-01T14:',
        '',
        'asdf',
        '01/01/2013',
    ]

    for bad_interval in bad_intervals:
        yield (
            assert_raises,
            Exception,
            inputs.iso8601interval,
            bad_interval,
        )