Ensures :attr:`subject` is less than *other*.

def is_less_than(self, other):
        """
        Ensures :attr:`subject` is less than *other*.
        """
        try:
            unittest_case.assertTrue(self._subject < other)
        except self._catch as err:
            raise self._error_factory(_format("Expected {} to be less than {}", self._subject, other))
        return ChainInspector(self._subject)