def __init__(self, package, version):
        """Construct a new requirement.

        :param package: the package name.
        :param version: a semver compatible version specification.
        """
        self.package = package
        self.version = version
        if self.version and not re.match(r"[<=>~]", version[:2]):
            self.version = "=={}".format(self.version)
def call_process(cls, cmd):
        if cls.is_error:
            raise subprocess.CalledProcessError(-1, cmd=cmd, output="Couldn't call xset.")

        if cmd[1:] == ["q"]:
            track = cls.info[cls.index]
            output = "\n".join(track)
            return output