How to use the certbot.errors.CertStorageError function in certbot

def _check_symlinks(self):
        """Raises an exception if a symlink doesn't exist"""
        for kind in ALL_FOUR:
            link = getattr(self, kind)
            if not os.path.islink(link):
                raise errors.CertStorageError(
                    "expected {0} to be a symlink".format(link))
            target = get_link_target(link)
            if not os.path.exists(target):
                raise errors.CertStorageError("target {0} of symlink {1} does "
                                              "not exist".format(target, link))

"""The filename that corresponds to the specified version and kind.

        .. warning:: The specified version may not exist in this
           lineage. There is no guarantee that the file path returned
           by this method actually exists.

        :param str kind: the lineage member item ("cert", "privkey",
            "chain", or "fullchain")
        :param int version: the desired version

        :returns: The path to the specified version of the specified member.
        :rtype: str

        """
        if kind not in ALL_FOUR:
            raise errors.CertStorageError("unknown kind of item")
        where = os.path.dirname(self.current_target(kind))
        return os.path.join(where, "{0}{1}.pem".format(kind, version))

def lineage_for_certname(cli_config, certname):
    """Find a lineage object with name certname."""
    configs_dir = cli_config.renewal_configs_dir
    # Verify the directory is there
    util.make_or_verify_dir(configs_dir, mode=0o755)
    try:
        renewal_file = storage.renewal_file_for_certname(cli_config, certname)
    except errors.CertStorageError:
        return None
    try:
        return storage.RenewableCert(renewal_file, cli_config)
    except (errors.CertStorageError, IOError):
        logger.debug("Renewal conf file %s is broken.", renewal_file)
        logger.debug("Traceback was:\n%s", traceback.format_exc())
        return None

def current_version(self, kind):
        """Returns numerical version of the specified item.

        For example, if kind is "chain" and the current chain link
        points to a file named "chain7.pem", returns the integer 7.

        :param str kind: the lineage member item ("cert", "privkey",
            "chain", or "fullchain")

        :returns: the current version of the specified member.
        :rtype: int

        """
        if kind not in ALL_FOUR:
            raise errors.CertStorageError("unknown kind of item")
        pattern = re.compile(r"^{0}([0-9]+)\.pem$".format(kind))
        target = self.current_target(kind)
        if target is None or not os.path.exists(target):
            logger.debug("Current-version target for %s "
                         "does not exist at %s.", kind, target)
            target = ""
        matches = pattern.match(os.path.basename(target))
        if matches:
            return int(matches.groups()[0])
        logger.debug("No matches for target %s.", kind)
        return None

def current_version(self, kind):
        """Returns numerical version of the specified item.

        For example, if kind is "chain" and the current chain link
        points to a file named "chain7.pem", returns the integer 7.

        :param str kind: the lineage member item ("cert", "privkey",
            "chain", or "fullchain")

        :returns: the current version of the specified member.
        :rtype: int

        """
        if kind not in ALL_FOUR:
            raise errors.CertStorageError("unknown kind of item")
        pattern = re.compile(r"^{0}([0-9]+)\.pem$".format(kind))
        target = self.current_target(kind)
        if target is None or not os.path.exists(target):
            logger.debug("Current-version target for %s "
                         "does not exist at %s.", kind, target)
            target = ""
        matches = pattern.match(os.path.basename(target))
        if matches:
            return int(matches.groups()[0])
        else:
            logger.debug("No matches for target %s.", kind)
            return None

"""What are the subject names of this certificate?

        (If no version is specified, use the current version.)

        :param int version: the desired version number
        :returns: the subject names
        :rtype: `list` of `str`
        :raises .CertStorageError: if could not find cert file.

        """
        if version is None:
            target = self.current_target("cert")
        else:
            target = self.version("cert", version)
        if target is None:
            raise errors.CertStorageError("could not find cert file")
        with open(target) as f:
            return crypto_util.get_names_from_cert(f.read())

def renewal_file_for_certname(config, certname):
    """Return /path/to/certname.conf in the renewal conf directory"""
    path = os.path.join(config.renewal_configs_dir, "{0}.conf".format(certname))
    if not os.path.exists(path):
        raise errors.CertStorageError("No certificate found with name {0} (expected "
            "{1}).".format(certname, path))
    return path

def _update_link_to(self, kind, version):
        """Make the specified item point at the specified version.

        (Note that this method doesn't verify that the specified version
        exists.)

        :param str kind: the lineage member item ("cert", "privkey",
            "chain", or "fullchain")
        :param int version: the desired version

        """
        if kind not in ALL_FOUR:
            raise errors.CertStorageError("unknown kind of item")
        link = getattr(self, kind)
        filename = "{0}{1}.pem".format(kind, version)
        # Relative rather than absolute target directory
        target_directory = os.path.dirname(os.readlink(link))
        # TODO: it could be safer to make the link first under a temporary
        #       filename, then unlink the old link, then rename the new link
        #       to the old link; this ensures that this process is able to
        #       create symlinks.
        # TODO: we might also want to check consistency of related links
        #       for the other corresponding items
        os.unlink(link)
        os.symlink(os.path.join(target_directory, filename), link)

# self.configuration should be used to read parameters that
        # may have been chosen based on default values from the
        # systemwide renewal configuration; self.configfile should be
        # used to make and save changes.
        try:
            self.configfile = configobj.ConfigObj(config_filename)
        except configobj.ConfigObjError:
            raise errors.CertStorageError(
                "error parsing {0}".format(config_filename))
        # TODO: Do we actually use anything from defaults and do we want to
        #       read further defaults from the systemwide renewal configuration
        #       file at this stage?
        self.configuration = config_with_defaults(self.configfile)

        if not all(x in self.configuration for x in ALL_FOUR):
            raise errors.CertStorageError(
                "renewal config file {0} is missing a required "
                "file reference".format(self.configfile))

        self.cert = self.configuration["cert"]
        self.privkey = self.configuration["privkey"]
        self.chain = self.configuration["chain"]
        self.fullchain = self.configuration["fullchain"]
        self.live_dir = os.path.dirname(self.cert)

        self._fix_symlinks()
        self._check_symlinks()

def lineagename_for_filename(config_filename):
    """Returns the lineagename for a configuration filename.
    """
    if not config_filename.endswith(".conf"):
        raise errors.CertStorageError(
            "renewal config file name must end in .conf")
    return os.path.basename(config_filename[:-len(".conf")])