How to use the everett.manager.ConfigEnvFileEnv function in everett

def test_ConfigEnvFileEnv(datadir):
    env_filename = os.path.join(datadir, ".env")
    cefe = ConfigEnvFileEnv(["/does/not/exist/.env", env_filename])
    assert cefe.get("not_a", namespace="youre") == "golfer"
    assert cefe.get("loglevel") == "walter"
    assert cefe.get("LOGLEVEL") == "walter"
    assert cefe.get("missing") is NO_VALUE
    assert cefe.data == {
        "LOGLEVEL": "walter",
        "DEBUG": "True",
        "YOURE_NOT_A": "golfer",
        "DATABASE_URL": "sqlite:///kahlua.db",
    }

    cefe = ConfigEnvFileEnv(env_filename)
    assert cefe.get("not_a", namespace="youre") == "golfer"

    cefe = ConfigEnvFileEnv("/does/not/exist/.env")
    assert cefe.get("loglevel") is NO_VALUE

cefe = ConfigEnvFileEnv(["/does/not/exist/.env", env_filename])
    assert cefe.get("not_a", namespace="youre") == "golfer"
    assert cefe.get("loglevel") == "walter"
    assert cefe.get("LOGLEVEL") == "walter"
    assert cefe.get("missing") is NO_VALUE
    assert cefe.data == {
        "LOGLEVEL": "walter",
        "DEBUG": "True",
        "YOURE_NOT_A": "golfer",
        "DATABASE_URL": "sqlite:///kahlua.db",
    }

    cefe = ConfigEnvFileEnv(env_filename)
    assert cefe.get("not_a", namespace="youre") == "golfer"

    cefe = ConfigEnvFileEnv("/does/not/exist/.env")
    assert cefe.get("loglevel") is NO_VALUE

def test_ConfigEnvFileEnv(datadir):
    env_filename = os.path.join(datadir, ".env")
    cefe = ConfigEnvFileEnv(["/does/not/exist/.env", env_filename])
    assert cefe.get("not_a", namespace="youre") == "golfer"
    assert cefe.get("loglevel") == "walter"
    assert cefe.get("LOGLEVEL") == "walter"
    assert cefe.get("missing") is NO_VALUE
    assert cefe.data == {
        "LOGLEVEL": "walter",
        "DEBUG": "True",
        "YOURE_NOT_A": "golfer",
        "DATABASE_URL": "sqlite:///kahlua.db",
    }

    cefe = ConfigEnvFileEnv(env_filename)
    assert cefe.get("not_a", namespace="youre") == "golfer"

    cefe = ConfigEnvFileEnv("/does/not/exist/.env")
    assert cefe.get("loglevel") is NO_VALUE

config_file_locations = self._discover_config_file_locations(profile)

        help_doc = ('Check https://docs.rastervision.io/ for docs.')
        self.config = ConfigManager(
            # Specify one or more configuration environments in
            # the order they should be checked
            [
                # Allow overrides
                ConfigDictEnv(config_overrides),

                # Looks in OS environment first
                ConfigOSEnv(),

                # Look for an .env file
                ConfigEnvFileEnv('.env'),

                # Looks in INI files in order specified
                ConfigIniEnv(config_file_locations),
            ],

            # Make it easy for users to find your configuration docs
            doc=help_doc)

def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self.ENVIRON = EnvironProxy(
            ConfigManager(
                [
                    ConfigOSEnv(),
                    ConfigEnvFileEnv(".env"),
                    DumbConfigIniEnv([os.environ.get("ARA_CFG"), "~/.config/ara/server.cfg", "/etc/ara/server.cfg"]),
                ]
            ).with_namespace("ara")
        )

if builds < min_builds:
        raise ValueError('Too few builds for {}'.format(version_key))


def validate_data():
    for key in FIREFOX_VERSION_KEYS:
        count_firefox_builds(key)

    for key in THUNDERBIRD_VERSION_KEYS:
        count_thunderbird_builds(key)


# setup and run

config = ConfigManager([ConfigOSEnv(),
                        ConfigEnvFileEnv(path('.env'))])
settings.configure(
    DEBUG=False,
    PROD_DETAILS_DIR=path('product-details'),
    PROD_DETAILS_URL=config('PROD_DETAILS_URL',
                            default='https://product-details.mozilla.org/1.0/'),
    PROD_DETAILS_STORAGE='product_details.storage.PDFileStorage',
    INSTALLED_APPS=['product_details'],
    # disable cache
    CACHES={'default': {'BACKEND': 'django.core.cache.backends.dummy.DummyCache'}},
)
django.setup()

from product_details import product_details as pd  # noqa

if __name__ == '__main__':
    update_data()

This is shorthand for::

            config = ConfigManager(
                environments=[
                    ConfigOSEnv(),
                    ConfigEnvFileEnv(['.env'])
                ]
            )


        :arg env_file: the name of the env file to use

        :returns: a :py:class:`everett.manager.ConfigManager`

        """
        return cls(environments=[ConfigOSEnv(), ConfigEnvFileEnv([env_file])])

from pathlib import Path

from everett.manager import ConfigManager, ConfigEnvFileEnv, ConfigOSEnv, ListOf
import django_cache_url


ROOT_PATH = Path(__file__).resolve().parents[1]


def path(*paths):
    return str(ROOT_PATH.joinpath(*paths))


config = ConfigManager([
    ConfigEnvFileEnv(path('.env')),
    ConfigOSEnv(),
])


# Build paths inside the project like this: path(...)
BASE_DIR = str(ROOT_PATH)

# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/1.8/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = config('SECRET_KEY')

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = config('DEBUG', default='false', parser=bool)