def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
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