def _get_bucket(self):
        '''get a bucket based on a bucket name. If it doesn't exist, create it.
        '''

        # Case 1: The bucket already exists
        try:
            self._bucket = self._bucket_service.get_bucket(self._bucket_name)

        # Case 2: The bucket needs to be created
        except google.cloud.exceptions.NotFound:
            self._bucket = self._bucket_service.create_bucket(self._bucket_name)

        # Case 3: The bucket name is already taken
        except:
            bot.error('Cannot get or create %s' %self._bucket_name)
            sys.exit(1)

        return self._bucket
get a bucket based on a bucket name. If it doesn't exist, create it.