def parse_lock(self):
        """Parses app lock file

        :return: Details about last update
        """
        try:
            with open(self.lock_file, "r") as reader:
                data = json.loads(reader.read())
                self.last_update = datetime.datetime.strptime(
                    data["last_update"],
                    AppCronLock.DATETIME_FORMAT
                )
        except:  # malformed lock file
            self.write_lock(last_update=datetime.datetime.fromtimestamp(0))
            self.parse_lock()
Parses app lock file

        :return: Details about last update