#
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# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
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#
#   http://www.apache.org/licenses/LICENSE-2.0
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"""Authentication backend"""
import logging
from importlib import import_module

from airflow.configuration import conf
from airflow.exceptions import AirflowConfigException, AirflowException

log = logging.getLogger(__name__)


def load_auth():
    """Loads authentication backend"""
    auth_backend = 'airflow.api.auth.backend.default'
    try:
        auth_backend = conf.get("api", "auth_backend")
    except AirflowConfigException:
        pass

    try:
        auth_backend = import_module(auth_backend)
        log.info("Loaded API auth backend: %s", auth_backend)
        return auth_backend
    except ImportError as err:
        log.critical("Cannot import %s for API authentication due to: %s", auth_backend, err)
        raise AirflowException(err)