def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
def _get_snapshot_status(self, snapshot_id):
        resp, body = self.get_snapshot(snapshot_id)
        status = body['status']
        # NOTE(afazekas): snapshot can reach an "error"
        # state in a "normal" lifecycle
        if (status == 'error'):
            raise exceptions.SnapshotBuildErrorException(
                snapshot_id=snapshot_id)

        return status