def __init__(self, package, version):
        """Construct a new requirement.

        :param package: the package name.
        :param version: a semver compatible version specification.
        """
        self.package = package
        self.version = version
        if self.version and not re.match(r"[<=>~]", version[:2]):
            self.version = "=={}".format(self.version)
def test_reverse_rfc822_datetime():
    dates = [
        ("Sat, 01 Jan 2011 00:00:00 -0000", datetime(2011, 1, 1, tzinfo=pytz.utc)),
        ("Sat, 01 Jan 2011 23:59:59 -0000", datetime(2011, 1, 1, 23, 59, 59, tzinfo=pytz.utc)),
        ("Sat, 01 Jan 2011 21:59:59 -0200", datetime(2011, 1, 1, 23, 59, 59, tzinfo=pytz.utc)),
    ]

    for date_string, expected in dates:
        yield assert_equal, inputs.datetime_from_rfc822(date_string), expected