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(cls, new_exiter_fun: Callable[[Optional[Exiter]], Exiter]) -> Iterator[None]:
        """Temporarily override the global exiter.

        NB: We don't want to try/finally here, because we want exceptions to propagate
        with the most recent exiter installed in sys.excepthook.
        If we wrap this in a try:finally, exceptions will be caught and exiters unset.
        """
        previous_exiter = cls._exiter
        new_exiter = new_exiter_fun(previous_exiter)
        cls._reset_exiter(new_exiter)
        yield
        cls._reset_exiter(previous_exiter)