def clean_semver(cls, version_spec):
        return re.sub(r"([<>=~])\s+?v?", "\\1", version_spec, re.IGNORECASE)
def check_bad_url_raises(value):
    try:
        inputs.url(value)
        assert False, "shouldn't get here"
    except ValueError as e:
        assert_equal(six.text_type(e), u"{0} is not a valid URL".format(value))