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 exiter_as_until_exception(
        cls, new_exiter_fun: Callable[[Optional[Exiter]], Exiter]
    ) -> Iterator[None]:
        """Temporarily override the global exiter, except this will unset it when an exception
        happens."""
        previous_exiter = cls._exiter
        new_exiter = new_exiter_fun(previous_exiter)
        try:
            cls._reset_exiter(new_exiter)
            yield
        finally:
            cls._reset_exiter(previous_exiter)