def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
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,
        )